Difference in performance between iOS devices

I'm developing a game for ios and notice surprising results performance-wise between my devices.

for example, my iphone 5 will perform better than my ipad mini retina. I really have no point of reference on how the two should compare. If they shared similar processor speeds, it would make sense that the ipad might suffer a performance problem since the textures are twice as big.. but I'm just guessing here.

When I look up processor speeds etc, I seem to find very general information (A6, or A7 processor). I'm looking for some easily understandable performance comparisons between devices so that I can predict which devices would perform better.