Yeah, they are both different beasts. The 500 IS an MPC, super portable, battery powered, and will become a collectible. I've never used any other MPC though, so other than the menu diving(which isn't that bad), I can't see the known shortcomings other people see in it. I just know it's a great machine and I have 3.

The best use of the 500 is plugging it up to the line-in on your car stereo, then mean mugging people at stop lights while finger tapping an ill beat.

For what it is though; I think the little mp is dope.

I've been using the SP 404 and the MPC 500 MIDI synced together, the SP for loops and the MPC for drums as it is a lot better for sequencing beats with, I got my OG 404 for 150 quid used and it's such a good set up if you can afford the extra. Really they are quite different machines but basically SP for looping MPC for beats in my opinion