I have some photos shot with my Canon 35mm and a prime lens that are hard to tell from MF up to about 8x10. After that however MF holds an advantage since film size becomes the limiting factor and lens quality less so. Obviously limiting the size of grain isn't necessarily the primary goal of photography so if you love your Leica and it allows you to make effective photos than there's really no argument here. There's no denying that 35mm is a vastly more capable format for many situations whether it be a Leica or whatever.