I will try an help you.
I own both and they are next to each other on my desk right now. Looking at them just now and writing this, i have to say the XL looks more chunky (first thing you notice).
My XL pads are raised slighty higher compared to my 2500.
The jacks on the back of the 2500 are nice and tight, whilst i find the XL's rear jacks are a little loose (you may comfirm if you wish), basically they can wobble a little. Not so on the 2500.
The sliders on the 2500 are very similar to the XL slider - no major difference.
The data wheel - XL has a smoother, quieter and super quick wheel over the clicky 2500 wheel which does not scroll as fast.
The LCD screen tilt - i find the 2500 LCD to tilt better and more solid / stable over the XL.
The buttons - XL and 2500 are on par, no real difference. The transport buttons on my XL are a little more 'fitted', whilst some of the 2500 buttons can be loose over the others.
Overall, the 2500 is well built and compares well to the XL. The 2500 can rattle on the bottom plate if you hit the pads really hard. The XL does not do this, but why smack the pads anyway?
Note: I have gone through 3 mpc 2500's (4 if you count a store demo unit) before being happy. In short the 1st and 2nd had proven faults.
If you are set on a 2500, dont let build quality stop you. Just buy from a reputable deal with a good policy.
