The PS3 has a total of 512MB of RAM. This limits how much information can be loaded when zoning into a zone or while navigating through a zone, limiting the number of player characters, enemies, terrain objects, etc. that the game can display at one time as all of this information has to be stored in the systems RAM. So while a PC user with plenty of RAM can see all player characters,mobs, terrain objects, effects of attacks/spells, etc. a PS3 user can only see as much as the RAM will allow to be loaded at one time.

That's pretty much the main factor holding back the game's potential on the PS3.