Hey Hog, thanks :).
The Honda was apparently quite a bit less peppy than the WR from my friend who rode both. He said the WR felt like the better bike on all counts (including suspension, which surprised me, because my forks and shocks are really in need of service). The CRF did seem a little anemic from what I could tell, but it also looked a little smaller, and it was described as a "mini bike" by the other two riders. I didn't want to deal with the rental repair fees, so I didn't have a chance to ride the CRF (I tend to tip over a lot in slow tough sections: I'm only 5'6").
I'd highly recommend taking the WR-- the trails are fun and you're always looking for a good line or a small wheelie. There are plenty of opportunities to take berms and small jumps (if you so desire). The ATVs may be just as fun but the good line can be very narrow :). I'd highly recommending doing the La Sal/Onion Creek loop, as well as White Rim Trail (clockwise, starting from Shafer trail). Let me know if you want my tracks (they have free campsites marked), I'd be happy to share good spots and approximate time/difficulties of each route.
Take a camera, and prepare to be blown away!