Canon 5D Mark III vs. 5DS R

I'm getting more into photography and it's time for an upgrade. I'd like an all-round camera that works well for portrait, landscape, as well as wildlife / action. I just had a 7D mark II but sent it back because I decided I want to go full-frame. Shooting in the jungle, the biggest concern is most often not enough light and I need to get acceptable pictures at 3200 or maybe even 6400 ISO.

I can get a used 5DS R for about the same price as a new 5D Mark III. But working with 50mp files seems to be a bit overkill, and the AF and speed seem to be slower on the 5DS R.

Any experiences with the two? I'm looking for top notch IQ and a reliable autofocus system. I have Canon glass so Nikon is too much of a hassle right now, although it would be cool to try them... Sony's cameras have the best sensors it seems, but they have much worse AF and seem unreliable when put to the test in the jungle.

I have never used the 5DS R but unless you are wanting the crazy high pixel count I would lean more towards a 5d iii.

I have the 5dsr and the 6d. the 6d has about the same sensor as the 5d3 but for only about $1400.
I have a few clients that print big so they need the 50mp and usually end up interpolating it much larger than that.
here are some full res samples I shot with the 5dsr..

http://www.felixtm.com/Canon-5dsr-sample-full-res/

Nice. Yeah, the resolution on the 5dsr would be really cool to have when shooting cities and landscapes... But, I would use it more for wildlife so ISO capabilities, speed, and autofocus are more important. I guess that makes the mark III the best choice (I want full-frame).