The sequencers on the 2000XL and 4000 are very similar.
However, the 2000XL only has 32Mb of Sample Ram - this is just a few seconds of CD Quality Sound. The 4000 on the other hand can go up to 512Mb - which is a damn sight more. Also, the 2000XL runs on either Zip Discs (100Mb Storage) - or, if they have not been upgraded, floppy discs(!) which can only hold 1.44Mb (and are SLOW as shit). The 4000 on the other hand has a 40Gig Hard Drive (which can be upgraded easily and cheaply). So storage space is not really a problem
The 4000 also has built in effects and a powerful filter. (Although you can purchase an FX board for the 2000XL from akai, but it's pretty pricey). Then again, you could easily use the effects on the motif6 / aw16g.
If you just want to do beats with the machine, then I would reccomend the 2000XL, it is cheaper and 32Mb is easily enough sampling time for drums on a track.
If, however, you want to get in depth and create some truley awsome sounds from the sampler (eg: the sound of a reversed bell, pitched down two octaves and played as a bassline...) then I would reccomend the 4000 instead.
So:
MPC2000XL PROs
o Cheaper
o Smaller footprint.
o Quieter (the 4000 makes an audiable whine from the hard disc)
MPC4000 PROs
o More sample Time (up to 512Mb)
o Huge internal Hard Disc for storage of samples / quicker access
o Big screen which makes editing waveforms easier.
o Powerful filters and FX unit.
jues
