One very small factor that might be worth considering.. At least it was for me.. They both work. I'm a big guy and even with a size too small I can get a front zip wetsuit off while wet or dry relatively easily (not as easily as a back zip, but no biggie). But the thing is, during surface intervals it's much easier to just zip it up and down, and if it's a slant style front zip it'll go down to your hip and you can pee without removing your suit. That's a big plus for me, I dunno about you guys, hehe.
I've even heard someone in this forum mention they have unsnapped the bcd and unzipped in the middle of a dive and went pee.. Doesn't seem too common, though, heh. but some people prefer the warmth it brings :worried: