For many critics and scholars, though, the distinctions are fairly superficial. Even ardent Mormons acknowledge some parallels.
Both Jeffs and Smith were considered by their respective communities to be prophets and both faced hostility within their own faiths and from outsiders. Each used religious language to describe and defend his multiple marriages. And much of each man's behavior was shrouded in secrecy.
Though he did reportedly take two 14-year-olds as "spiritual wives," Smith was not charged with marrying underage girls it wasn't widely known and the age of consent in much of America at the time was between 10 and 12.
Bigamy was a crime, though, and Smith was, by his own account, guilty of that.
So what are the differences between the two that make one a religious "genius," as literary critic Harold Bloom described Smith, and the other a sexual predator and felon?
For Sarah Barringer Gordon, it's obvious.
Smith was a charismatic, larger-than-life figure who was constructing an expansive theological, marital and economic universe, says Gordon, a legal expert and independent historian who has written extensively on Mormon polygamy. He was a visionary, while Jeffs "tried to replicate the life of a prophet," but was "twisted" in his approach to polygamy and to his people. He was "deeply destructive of other people and human dignity and even himself."
The LDS leader began his movement with no "religious mantle and spent his life creating one," says Gordon, a law professor at the University of Pennsylvania, "while Jeffs inherited a great deal of religious power and has spent his life exploiting it."
Still, questions about Smith's practice of plural marriage continue to vex even devoted Mormons.
Why, for instance, did Smith marry other men's wives? Was he motivated by religion or lust? And why are there so few documented offspring of his various unions?
There are, of course, no revealing audiotapes of Smith and his polygamous wives, no accounts of Smith offering sexual training or detailing reports of his supposed wedding nights.
A few letters, some oblique journal entries, speeches, official histories and memoirs written decades later offer tantalizing clues as to the Mormon founder's behavior, but decoding them largely depends on the assumptions one brings and what kind of weight one gives to defender or detractor accounts.
The issue of Smith's polygamy is, Mormon historian Richard Bushman says, "a Rorschach test" in which people see what they want to see.
And there is no one definitive answer.
LDS polygamy is born
By most accounts, Smith took his first official polygamous wife, Louisa Beaman, in 1841, although some historians believe he hinted at plural marriage or even practiced it much earlier.
At first, Smith told his burgeoning Mormon flock, he resisted God's command to follow the model of the biblical patriarchs. Eventually, he said, an angel with a raised sword compelled him to comply.
Smith asserted he was restoring extensive familial relationships just as he was trying to cut through centuries of Christian tradition with his new faith, The Church of Jesus Christ of Latter-day Saints. He was building Zion, he preached, ritually binding families and generations and raising up a "righteous seed."
To do that, he said, God authorized him to institute plural marriage.
In 1843, Smith dictated what he called a divine revelation that remains in LDS scripture, spelling out "a new and everlasting covenant" of plural marriage.
By the time of his death at age 38 in 1844, Smith had married secretly some 33 women between ages 14 and 50, says Todd Compton, author of In Sacred Loneliness: The Plural Wives of Joseph Smith.
Compton, who is LDS, does not believe Smith had sexual relations with the two 14-year-olds.
One of them, Helen Mar Kimball, wrote a memoir as an older woman about her "marriage" to Smith. It doesn't say whether she had sex, Compton says. "It's my interpretation of the evidence."
Brian Hales, a Mormon who is writing a two-volume work on Smith and his wives, believes Smith had sexual relations with nine of the 33 plural wives. Thirteen of the unions, he believes, were "eternal," not connubial.
"Claiming sexuality in more than nine plural unions," Hales writes,"goes beyond the evidence."
But Lawrence Foster, author of Religion and Sexuality: The Shakers, the Mormons, and the Oneida Community, sees no reason to believe that Smith wasn't fully involved with the women he chose as "spiritual wives."
"He was a handsome, dynamic leader with great physical and intellectual vitality a man not afraid to break with convention," Foster, who specializes in American religious history at Georgia Tech, writes in his book. "Many of his statements reveal a basically positive attitude toward sexual expression, as well as the difficulty he sometimes had in keeping his impulses in check."
Offspring and other men's wives
Many Mormons want to believe that Smith didn't have sexual relations with the women he took as plural wives. If the LDS prophet fathered nine children by his only legal wife, Emma, they reason, why are there so few documented offspring with the other 33 women?
Historians agree that at least two children were born of Smith's relations with women beyond his first wife, Compton says. But a key problem with documenting his progeny is that 14 of the so-called marriages were between women who were already married to other men, says George D. Smith, author of Nauvoo Polygamy: ' ... But We Called it Celestial Marriage.'
Latter-day Saints explain these relationships in two ways, says George Smith, himself a Mormon.
"Either the women must have separated from their husbands during the interval that Smith was married to them, then went back to them and continued to have children in their original families a fanciful explanation, I think," he says. "Or Smith is connected to these married women by 'celestial sealing,' which does not include sleeping together as man and wife."
To George Smith, neither explanation seems reasonable, but it is still curious why there were not more documented children.
Researchers have suggested eight possible offspring from Joseph Smith's plural wives, Hales says, but DNA testing on descendants has failed to prove any link. So, he argues, Smith must not have had frequent sex with too many of the women, who were young and likely fertile.
That may be, Foster says, because of Smith's extensive leadership obligations and the prying eyes of friends, neighbors and especially Emma.
So how did he persuade monogamous men and women in a puritanical society to go along with his plan for multiple marriage partners?
Talk and tactics
Smith preached fervently and frequently about the nature of the family, including extensive relations between generations, righteous "dynasties" and "adopted" friends. It was at the core of his theology.
Jeffs sermonized about that, too, but also trained women in the Fundamentalist Church of Jesus Christ of Latter-Day Saints in ways to please him sexually during what he called "heavenly sessions."
Hales and other LDS historians believe Smith's intimate relations were about procreation, not sexual satisfaction. They claim Smith did not talk openly about his own pleasure.
Nonsense, says Foster.
"Joseph Smith did talk quite a lot about sex, even if some of the later records have been cleaned up quite a bit. One of the most common code words for plural marriage was that it was a man's 'privilege' and Joseph told one follower that 'it is your privilege to have as many wives as you want.' "
Still, Foster says, Smith largely couched his proposals in religious terms.
Smith proffered a promise of salvation and even told 14-year-old Helen Mar Kimball that it would extend to her entire family if she complied.
Smith "skillfully used a wide range of pressure tactics to try to convince women to become his plural wives," Foster says, "including threatening them with perdition if they wouldn't go along with him."
"The gate [to salvation] will be forever closed against you," Foster says Smith told one woman if she refused him.
Nancy Rigdon, daughter of Smith's counselor Sidney Rigdon, was furious at the Mormon prophet's proposal to her, Compton says.
Hales argues that most of the women Smith approached were free to reject him and some did. None, Hales says, even the seven who abandoned their LDS faith, ever spoke ill of him or their relationship.
"Decades after their feelings had matured and their youthful perspectives expanded by additional experiences with marriage and sexual relations, none of them claimed they were victimized or beguiled by the prophet," Hales says. "None came forth to write an exposé to tell the world he was a seducing imposter. None wrote that Joseph Smith's polygamy was a sham or a cover-up for illicit sexual relations."
Building a society
Ultimately, the difference between Smith and Jeffs may rest in the movement they spawned.
Even as he was taking more wives for himself, Smith was introducing a theological system in which women played a central role. He helped create a women's Relief Society and temple ceremonies in which men and women would rule over future generations as "kings and queens, priests and priestesses."
Smith drew other men around him, organizing them into leadership councils that provided some checks and balances, and even set up a system in which Smith himself could be tried and removed.
Some historians say Smith believing God ordered him to implement plural marriage without revealing details about how to do so struggled to heed the heavenly command. He tried to guarantee that every new marriage was "authorized" and that "sealings" were witnessed. In Nauvoo, Ill., however, it caused much consternation and chaos.
After Smith's death, friends and colleagues took the polygamy Smith introduced and brought it to Utah, giving it rules and making it more systematic. Smith's successor, Brigham Young, wanted parents and first wives to agree to any new marriage. Young also allowed unhappy polygamous wives to divorce or opt out of the system.
"These holy and sacred ordinances have nothing to do with whoredoms, unlawful connections, confusion or crime; but the very reverse," LDS apostle Parley P. Pratt wrote in 1845. "They have laws, limits, and bounds of the strictest kind, and none but the pure in heart, the strictly virtuous, or those who repent and become such, are worthy to partake of them. And … [a] dreadful weight of condemnation await those who pervert, or abuse them."
Meanwhile, the Mormon community was expanding with each new wave of converts and reaching out across the globe. In 1890, the Salt Lake City-based faith ended polygamy.
Starting with Jeffs' father, Rulon, the FLDS did away with quorums and councils that could check his decisions and power, Watson says. Since taking over in 2002, Jeffs has pushed his flock into increasing isolation, pulling children out of schools, moving the group to Texas, expelling critics, limiting access to technology and pushing them to groom themselves in a uniform fashion.
Even among the FLDS, Jeffs is an aberration, says Ken Driggs, an Atlanta defense attorney who has many friends in the polygamous community and has written about it extensively since 1988.
"I can't imagine the conditions under which Jeffs' conduct as described at trial would be accepted by the FLDS," Driggs says. "They are generally honest, moral, sexually conservative people. I never observed anything that even hinted at the kind of things testified to at trial."
Many among the FLDS faithful will, no doubt, continue to defend their leader, seeing Jeffs as God's mouthpiece. They may even view him as a martyr, jailed for his faith.
It remains to be seen whether his brand of polygamy will create a vibrant, global faith or shrink to nothing. Only then might the comparison with Mormonism's founder be clear.
Joseph's young wives
Author Todd Compton's list of 33 plural wives of Joseph Smith includes 10 women under age 20.
Helen Mar Kimball, 14
Nancy M. Winchester, 14
Flora Ann Woodworth, 16
Sarah Ann Whitney, 17
Sarah Lawrence, 17
Lucy Walker, 17
Fanny Alger, 16-19
Emily Dow Partridge, 19
Maria Lawrence, 19
Melissa Lott, 19