I have Yosemite and El Capitan on two separate 250GB Samsung Evo 850 SSD's connected to a Gigabyte GA-Z97X-UD5H board, intel i7 4770k cpu, 16MB of 1600MHz ram, two Nvidia 660 GTX graphics cards, I have not overclocked the cpu or memory. I texted both OS installations with the Geekbench 32-bit software the results were surprising!
Yosemite has the better 32-bit benchmark, see attached image. This image shows the benchmark score for the two OS's on the same machine. The single core difference is marginal but the multicore score is a good 5% lower on El Capitan.