as a person who went PS3 to PS4, I can state there are a few things that are diff between both versions: Resolution detail (Texture & draw distance), number of players visable at once (good luck making to a Zerged hunt & seeing it on PS3), speed of information loading (also affecting previous example with Hunts), Effects & slight animations (the shine from gather nodes is dimmer on PS3, also "Jiggle-physics" aren't used on PS3 but are on PS4 then there the shine effect they added to floors in 3.3 that PS3 can't have)
I doubt the PS3 is acutually "Holding us back" like said (as the game is only slightly diferent between PS3 & PS4 but its still playable on PS3 (u just miss out on "Fluff" effects is all) I thinks its more SE & Dev's atempts to keep the only diff being these "fluff" effects (look at the diff between DA: Inquision, PS4 just has more background NPC's & stuff when it ant a cutscene both are playable just 1 "looks" cooler due to having more "Fluff" is all))