I've never had an MPC. I have a Maschine, and it's fantastic.
The only thing I've heard is some vintage MPC's might apply saturation when you're sampling, but I can't confirm or deny this. Frankly, the Maschine seems better. And more producers have them than you may think. If you go on beatmakingvideos.com you'll usually find a lot of those producers have them.
The main benefit to Maschine for me was the samples, particularly the drums. I don't have to layer kicks very often with Maschine. They have a giant selection of drums, from 808's to vinyl's that sound ripped right off a mastered record.
Also, Native Instruments has a great collection of tutorial videos on Maschine. It's very intuitive.
Personally, I use it as a plugin in pro tools going through an aux channel for each pad. Maschine isn't exactly arrangement friendly, it's more about making loops (or at least if you can get it arrangement friendly, it's something I haven't learned yet) which you can drag into DAW's or bounce all files automatically. I prefer to just have a template in Pro Tools with 30 aux tracks for pads, then hidden audio files I can record the Auxes into. This allows me to do a few things.
1) Focus on the arrangement of a song more. I can just have maschine running on a loop and record my rap vox, and any transitions can be done after the fact or just recorded in one of those hidden audio tracks OR just recorded into a Pro Tools Instr track.
2) I like to keep everything mono except for maybe one instrument. Maschine's software doesn't play nice when I want almost everything mono. But if I want a bunch of things mono as a plugin in Pro Tools AND I want one thing stereo, that's easy to do as well.
3) I can unhide all of those audio tracks, hit record on all of them, play the beat, then I can consolidate all of those clips and bounce them to a mix session easy.
This should be easy to do in any DAW though, and is just one of many workflows you could have.
One last thing, having Maschine can get you a discount on Komplete, which is what I got next. Ginormous selection of sounds and synths, you'll be able to cover lots of styles.