[twic]

> I'd rather have less MP if it means a better noise profile

In that case, you want the A7s. For some reason, there are three variants of the A7: the standard A7, with a 24 megapixel sensor, the A7R, with a 36 megapixel sensor (the R is for resolution, you see), and the A7s, with a 12 megapixel sensor, but better signal-to-noise ratio, and so low-light performance (the s is for sensitivity, you see - no idea why it's lowercase when the R is uppercase).

> and AFAIK there is a a fair amount of parameters affecting image quality other than the sensor itself.

I suppose the biggest one is the lens. The A7 doesn't have a big range of lenses yet, but there are a few made by Zeiss that are apparently very good.