Guys from What the A7 II like compare to the S and R?
I know S is the king for Low light
R is MP
what the A7 II
Also what is AF like on these for still shots/? I would of that Tracking won't be as fast as a 5D MKiii
The A7II is an update of the A7 with changes to the grip, shutter button placement and in body IS.
When the A7 and A7r came out I went for the A7 as I thought that 24mp would be enough for me coming from Canon 20D and 5D. I didn't think that I needed 36mp and I still don't think that I do. The A7 also has electronic first curtain shutter.... what that means I don't really care

but it makes the shutter a smidge quieter
I find the AF perfectly ok. People on line seem to whinge and wine but I don't have a problem but I don't use tracking and I'm happy with just one focus point. On the plus side there's no front / back focus or micro adjust silliness.
Ref. the earlier comment about the 6D being better in low light. This comparison site...
http://snapsort.com/compare/Canon-EOS-6D-vs-Sony-A7
...says "The 6D has a slight edge (0.1 f-stops) in low noise, high ISO performance" which I personally doubt is significant in the real world and there's also the question of noise reduction smearing v detail retention and I believe that the Sony is better than the Canon in that regard. I'd take the A7 and it's greater dynamic range (2.1 stops according to the link above and 10% better image quality, whatever that means and 20% more detail captured with the A7 too again according to that site.) over the 6D any day of the week. Actually another reason I'd not go for a 6D is that I like shooting with wide apertures and the 6D has a max shutter speed of 1/4000 which means using ND's or being limited to f2.8 or smaller whereas the A7 will shoot at 1/8000 and allows me to shoot with a 50mm f1.4 at f1.4 in good light.
If I had to go for a DSLR these days I'd go Nikon, Canon are too far behind the cutting edge these days IMVHO and although a lot of things wont matter in the real world IMVHO the extra dynamic range of the Sony chips does matter and Canon just can't compete with Sony and Nikon on DR..
One massive plus for me with the A7 and other mirrorless systems is that manual focus is a breeze and if you have the time for focus manually I think it's the way to go as with the magnified view it's like shooting macro at a distance and you can pick your point of focus more accurately than any auto focus system can. AF is fast and it'll focus on something but with manual focus and a magnified view you get to chose exactly what the point of focus is. AF just can't match that.
The A7 is the best cameras I've ever had and I'd have to have a gun put to my head before I went back to a Canon DSLR or indeed any conventional DSLR.