I got 1 3gb and few 6gb versions and there are some differences. When mining ethash they mine almost the same but for equihash I get 300 on 6GB vs 275 on 3GB with same clocks and tdp, on skein its 316 vs 280 and on lbry 3GB is also around 10% slower. I didn't configure them for max performance but more for optimal power to performance.