Gotta say I think lots has to do with your position on your bike, too. I have a more upright style bike with cruiser bars that I can be comfy on with anything wide enough and not too soft (Brooks B17 is perfect). For a more aggressive position I get pickier, and I find my chamois goes a long way to just holding my junk out of the way of my pendulum-ing thighs than providing any anti-chafe at all.

I love the Brooks line, in large part because the leather is smooth, and won't chafe without chamois. I still wear compression shorts with my Brooks Team Pro on my road bike, though, because I like the "support." I can't stand getting my nutzack pinched between saddle and thigh