Owning a pair of Margiela GATs now I have to say I like them better than my CPs. They are way more comfortable and somehow just have a slightly less boring look.
Although I think the construction of CPs is better, the sole ist studier and thicker and seems undestroyable whereas I'm really afraid of wearing the MMMs in the rain.
Maybe I just sized my CPs wrong, I normally wear 41 in most boots/shoes, while I think my "true size" is 41.5, my CPs are 40 tho. My MMMs are 41 and they fit perfect.