you do realize they are running at different clock speeds by default and before SLi is optimal you have to equally clock them.
using EVGA Precision or MSi Afterburner.?
the longer 570 with the fan in the back (also longer one right..?) well it exhaust heat outta the case and not in
the other 570 with the fan in the middle exhaust mostly out the back as well as the front, the heat coming out the back is going into your case.