Firstly the Leica S is the perfect camera for shooting fashion, why? Well I've used pretty much all the other makes of medium format camera to shoot fashion with and for me simplicity and ease of use is really important, obviously quality is too but you know with Leica you will have plenty of quality!
I first used a Hasselblad HD3II 50 system which is great quality, but really slow to use, the cameras battery grip is a little flimsy and the battery itself only lasts a couple of hours, where as the Leica S battery can shoot all day long no problem. I have also used Mamiya ZD system...