I played the disc version on both systems.
There's still the possibility that I'm blind. But I doubt it, with my history of PC gaming. A 10fps difference on AVERAGE would stick out like a sore thumb (unless it was between say 50 and 40, which for this type of game probably wouldn't look any different to most people).
iirc DF only tests cutscenes. I have noticed with a couple WiiU games, that framedrops often happen during cutscenes (Batman AC, AC3, Deus Ex) while i don't really notice them during gameplay. Might this be because the game is loading in the background? I don't know. But the same seems to be true for Splinter Cell, where DF tested cutscenes and Lens of Truth didn't, i think. And going by memory, the PS3 version of AC4 ran about 2-4 fps faster than WiiU, while the 360 version ran between 4 and 8 fps faster. Never 10, certainly not on average, and certainly not for PS3.