They couldn't be more different.
Georges St. Pierre is a chiselled physical specimen moulded by a youth spent in one of Montreal's toughest neighbourhoods. His conditioning is bulletproof, but holes in his mental game have dogged him since his title loss to Matt Serra.
B.J. Penn comes from a wealthy Hawaiian family and casts a shadow more reminiscent of Jell-O than granite. His training and commitment have been questioned, but his will and mental fortitude are unshakable.
The two champs' very distinct paths collide tonight when they face off for the UFC welterweight belt.
The main event at UFC 94 features St. Pierre's belt on the line as the lightweight Penn steps up a weight class.
St. Pierre, who speaks in well-rehearsed cliches since taking up with a sports psychologist, clings to his "poker players don't reveal their cards" mantra in the pre-fight hype.
Coming off four dominant victories, St. Pierre (17-2) has shown a solid wrestling base that has allowed him to control his opponents, complemented with explosive fits of ground-and-pound that have become signature components of his attack.
St. Pierre is quick to dismiss the notion he is inventing his own martial art.
"It's not Georges-jitsu," says the 27-year-old. "It's not my own martial art. I train wrestling with Olympians. I train boxing with some former world champions. It's about training the best disciplines with the best guys."
Since joining Greg Jackson's team in New Mexico, St. Pierre has looked indestructible.
TRAINED FOR 'AN ARMY'
He has beaten the top 170-pounders: Matt Hughes, Jon Fitch, Josh Koscheck and a victory over Serra before a hometown crowd of 20,000-plus to recapture the belt.
St. Pierre vows his four-fight win streak won't come to an end at the hands of Penn.
"I've trained to fight an army," says St. Pierre.
Penn says his game plan is clear: Break St. Pierre's "fragile" will.
"He's going to try to kick me hard, he's going to try to punch me hard, he's going to try to throw me on my head," says Penn (13-4-1).
"He's going to try to push through my half-guard and pound me and push me until I get tired.
"He's tough, but once I get through all that, he's empty on the inside and that's how I'm going to finish him."
It's a dream matchup, says UFC president Dana White.
"You're lucky if you get to see three or four of these fights in a lifetime. Two of the best fighters in the world. Both champions are in their prime."
As for St. Pierre getting a shot at Anderson Silva's middleweight crown if he beats Penn, White says: "Anything's possible, but he has to face Thiago Alves first."