I would put my money on the A7C being more reliable than any Leica digital M body. The A7C body also seems to be very well built. From DPReview:
"Although it looks a lot like an a6000-series model, the a7C itself feels extremely rugged in a way that those cameras don't. It's housed in what Sony calls a magnesium alloy monocoque: a combined, single-piece chassis and shell, akin to what US car-makers would call 'unibody' construction. This ensures there's no flex or give anywhere in the camera. It also means there are fewer body seams to seal against the elements."