Tank and Ken were probably both at their peaks in overall skill at the Ultimate Ultimate 96, but Ken was superior. Ken's chin was hard as fuck back in the day and Tank didn't have the gas tank to hang with Ken deep into a fight. Despite Ken's cardio being very poor in his post WWF run, his cardio was GREAT during his first UFC run.
Tank was an underrated wrestler and was very big, but he didn't have the speed or agility to match Ken's athleticism. Ken would have taken Tank down at some point in the fight; Ken was a master at timing takedowns at exactly when his opponent was off balance throwing a punch or kick, and was great at getting inside for a takedown while avoiding being hit. When Tank commits heavily to a KO punch, that is exactly when Ken is going to go for the takedown, and Ken's ridiculous speed and strength would make the takedown successful.
At the UU96, Ken shot one of the fastest takedowns I've ever seen a heavyweight shoot in MMA, when he shot that perfectly timed double leg on Brian Johnston after Johnston threw a kick. Maurice Smith said one time that if you blinked, Ken would have you on your back; that's how fast Ken's takedowns were. We saw exactly this at the UU96. We didn't see this too often earlier in his UFC career because Ken was ALWAYS dealing with some sort of knee injury, which slowed his takedowns considerably.
In addition, Ken was an underrated clinch fighter; Dan Severn abused Tank in the clinch in their fight at the first Ultimate Ultimate, while Severn couldn't move Ken in the clinch at UFC 6. So if the fight ends up in the clinch, I expect Ken to have the advantage here, too.
Tank wore shoes, too, so it would be easy for Ken to break Tank's leg if it went to the ground.
I also question whether Tank genuinely disrespects Ken as much as he says he does. Tank was a smart guy and Ken was the top dog when Tank broke into the UFC. When Tank called Ken out at the first Ultimate Ultimate in 1995 for not fighting in the tournament (Tank said something like "all the real fighters are here fighting in the tournament"), Ken was the champion and Tank was gunning for him. Ken was a complete psycho and Tank's trash talking made Ken irate (especially when Tank called Bohlander a "pussy" for pulling out of the tournament with an injury before their fight, despite Tank outweighing Jerry by like 70 lbs.), so the rivalry was definitely real, but I wonder if Tank really didn't respect Ken as a fighter. He had to have.
After Ken challenged Tank in his postfight interview at the UU96, Tank responded to the challenge live at UFC 12 when Bruce Beck asked him about it; Tank declined the fight and said something like "Ken should go look in the mirror and challenge himself, Ken's not on my agenda", so if he felt that Ken was such a fake fighter I question why he didn't accept the fight. Tank also turned down a fight with Ken at UFC 48, where Ken fought Kimo instead, but (IIRC) this was around the time that Tank's mother died and Tank was in no condition to fight anybody.