P90 or UMP45? Which one is better?

I like the UMP45 the most on paper, but enjoy the P90 a little bit more. I like the UMP45 in that once you add Rapid Fire it outdoes every other SMG on the game in every catagory and i normally do well with it, and i know a lot of people dedicated to the P90 and i guess with stopping power its a great SMG, but what would be the attachment for it? I'm kinda lost in this certain aspect of my SMG cl.