A7s or D610/D750 weddings etc.

Hello this is my first post on the forum. I'm thinking of buying a new camera. Until now I operate a canon 5d.

I would use it if necessary to wedding photography and reportage, but it is not my main profession (rather supplement, hobby). If I were a professional to take care of wedding photography probably i will go for the Nikon D750, but I wonder a little.

Sony at once more expanding system (new 50 1.8). I think of sony A7S but I'm afraid of lenses and autofocus. Adapter la-ea4 - but how to cope in low light? The iso is  not a problem, because sonya7s in this respect is great and has silent shutter mode, the next downside is single SD card slot. I do not know what to do.

Does anyone have a comparison of how the autofocus with the old Minolta lenses rokkor and adapter la-ea4 compared to the Nikon D610 in low light - comparatively better, worse? Certainly can not measure the D750 ... Sorry for my potato english and again hello!