I agree with Mexikatz, Couture, was always one of my favorite fighters, but he's way past his prime.
Anyway, he doesn't have the punching power to "Lucky Punch" a big guy like that. Lidell did. Couture, is a ground and pound type of guy and Lesnar is way to big for that and handles himself very well on the mat.
The most impressed that I've ever been with Couture is when we he beat Belfort, but that was a long time ago, back in 1996 I think, even then, Vitor is about the size of a lt. heavy.
No where near 265! And he's not a David Tank Abbot 265 either.
It's a good match up though, because Lesnar has a lot to learn still, and this fight is evenly matched.
It would be a good win for either fighter. It will help one fighter come in, keep another from getting pushed out. Definately more interesting than the Spider Silva match. I have to go with Lesnar.