I decided to look at this from a personal point of view - like I wouldn't. Anyway, I was never that big a fan of Benoit. Say I am and you've just imagined something I've written. The only time I've ever talked about him is the time he murdered his wife and child, that's how bland I found him. Sure, he was a good wrestler, but everything else about him I just really didn't get.
Lesnar, on the other hand, was one of my favourites for a time, and still is really. Here was a guy like Batista - uh-oh! Crap wrestler alert! He could move and wrestle as well as, say, Kurt Angle though. The guy that was a monster that delivered in every department, save the microphobe. Here's a guy that could survive a botched Shooting Star Splash, landing on his head and neck.
As a matter of personal preference, I pick Lesnar. As for who would win the match, I'd also go for Lesnar. There are three people I would legitimately buy into being dangerous in the ring. One's Kurt Angle, one's Dean Malenko (a new addition) and one's Brock Lesnar.