I have chronic bouts of automotive OCD, so when I was making this decision myself, I just could not deal with how clearly less than perfect the fitment of m3 reps on 335's looked to me. While the misalignment is slight at worst, I could still see it in every single picture I saw of the m3 reps, and it drove me nuts.
My vote is M-tech; more aggresive than stock, but just subtle enough to not say "I bought these skirts seperately and put them on after I bought the car". I know a lot of ppl will disagree but hey, it's your call, both are a major improvement to the flat oem skirts.
No doubt, the m3 reps are much more aggresive looking so if that's your goal, it's a clear winner. I just think that the curves of the m3 skirt styling coordinated with the wider fender flares of the m3 perfectly and unless your 335 has very aggresive modifications, it doesn't mesh as perfectly.