The 1K can do more...but the XL seems easier to me.
Sound
The sound on the 1000 is thinner to me than the XL. The highs seemed harsh and the low end just doesn't have as much punch as the XL. My ears, my opinion.
Effects
I don't have the effects card on my XL so I can't compare the effects.
Pads
We all know - XL is better. One thing people tend to forget when it comes to instruments (computer, guitar, or MPC) is that ergonomics is important. The XL has a surface area that is very ergonomic, the XL is less and computers...let's face it you're limited to a keyboard and mouse. People who say the prefer something to hit on versus using a mouse are really saying that ergonomics are important. This is probably one reason why Rolands MC909 and SP series samplers couldn't compete with Akai.
XL is for those producers who not what they're gonna do...
Good Low End Filter, Sequencer, Basic Sample Editing and Drum Production = XL
MPC 1000 is for those who aren't as sure but want all options available....
Experiementation, Effect, Vocal Sampling, Portability = 1K
Cool G Money