I've never tried either, so I can't say for sure, but it seems to me that when you are developing a game you are familiar with all the code from the ground up, but when porting you have to analyze, modify, and patch it to make it work with a different system. It's hard to say where the comparable difficulty between the two tasks lay. There's also the possibility that EA didn't particularly care about the quality of their ports as opposed to their own titles.