Well, aside from the obvious geometric differences

there's this
http://www7a.biglobe.ne.jp/~mpc1000/chart.htmbut what that means in practice, idk - if someone more versed could speak on that it be useful
I went straight from 1 to 2XL, primarily because recording q-link changes was how I thought it
should be in 2XL but the CHORD and ARPEG functions are, for me, a real bonus that make the MPC more of a versatile instrument.
Going by the chart OS2 has the following that OS2xl doesn't
*Extra Audio Play (Audio Time Stretch & Pitch Shift)
*Grid Edit (DRUM) 6PAD Mode
*Grid Edit Q-Link Real Time
*Grid Edit (DRUM) Loop Edit Mode
*Start offset of a sample (Audio Track)
*Pan in Q-Link NOTE ON
I have no idea what Grid Edit (DRUM) Loop Edit Mode is and this video doesn't really help
http://www.youtube.com/watch?v=6GFD3vThhAkThat aside - the only thing there I'd like is q-link panning
If you look at the chart, the amount and quality of feature you gain on xl is greater than what you loose, but there is something about the q-links between 2 and 2xl that is different - maybe you can only record 1 at a time or something, idk
I love the MAIN screen on xl, really helps with editing. I'm still learning basic functions but the work flow on xl is so much slicker than OS1.
If you have xl you can flip between 2 and XL, but when I flipped between 1 and 2 (trial) all my auto-load folders got messed up which kinda detered me from doing it often...