Hmmm. Well first and foremost we can start with High Definition textures. These will take up more RAM for the game to process visually along with character models etc. The amount of objects (player characters, NPC, terrain objects, decorations, etc.) in any given area could be limited by the low amount of RAM available in the PS3 as SE wants everyone to have an equal experience when playing the game. The amount of items available to be visible on a character model would be limited by the small amount of RAM, character creation options which if more options were added would cause each character to take up more RAM, just anything that you can think of that's going to take memory for the game to display is going to be limited by the 512MB of RAM available in the PS3.

Again, with SE wanting everyone to have the same, or nearly the same, experience while playing the game, SE will not add things that people with more RAM can benefit from to the point that it gives a PC or PS4 player an advantage or a much better gameplay experience compared to a PS3 player.