Whats the best folding GPU

[Trunkey]

As per the title if I wanted to build a straight folding rig what is the best GPU to install?
Helpful if you can tell me why too please.

Thanks.

 

[Trunkey]

I have a water cooled R9 290x but are some of the CAD cads going to be better than that and a Titan x ??

 

[Trunkey]

Ppd are low because that's a Mac folding on just an i5 CPU.
My pc chucks out around 280k ppd folding on a different team.
I'm looking to build a matx system for the fun of it and that will also be folding 24/7 but not used for any serious gaming.
I have a spare R9 270x lying about so might use that but was just wondering what the other options were.