I'm trying to figure out which fenders I should buy for my new Trek 4900. I originally wasn't going to bother with them, but after riding around a wet campus yesterday I noticed my backpack had a nice black streak going right down the middle from nasty slush being spit up on it. Anyway, after searching around I've found a couple different options that could work. Firstly are some fenders by Topeak. These seem to be mentioned quite a bit on the forums, so I assume they're a good choice. The next option is from Mud Machine (www.mudmachine.com). Their rear fender bolts onto the v-brake mounts instead of the seat post. It looks like this would make the fender a little more low profile, but I'm not sure whether it would have a good or bad effect on its performance. What do you guys think?

P.S. I should also point out the Mud Machine fenders are significantly more expensive than any others I've seen. Not sure if this is because of a higher quality product or just overpriced.