Well, I still one or two shot mobs, cast fast, and kill elites fast, how that is unlikely to get more loot on mp5 than on mp1 if mp5 just has more loot? It also has more exp% and more MF, so I don't see a math problem here.
The bonuses for MP5 is not big enough, to make up for big ammount of mobs less killed compared ie mp1. Its something you really need to understand. Because you get ie 60 extra MF, and a tad bigger chance to receive a extra drop on MP5, is nowhere near a big enough compensation, for the less ammount of mobs you will kill. And the more you raise the MP the more your getting punished dropwise per hour.