There's things I prefer about mp10, but they're both great figures. I like that the newer one is 98% plastic, and therefor not so heavy when messing about with. The only diecast in him is thevarm that connects to his botmode grill.
However, I love the features on mp01, like his suspension, opening leg vents, light up matrix chamber ect.
However, mp10 wins in altmode. He hasn't got the arm joints blatantly showing, and is generally a better shape
Saying that, I still wanna get a mp04 at some point