That's a super tuff call to make, I know, I had to make the exact same 
choice. In the end, I obviously bought an XL7 over the MPC2k. They both have 
so many good and bad points to there sequencing capabilities, that they 
nearly cancel each other out....there are a few major differences that 
helped me make my decision though....

the xx-7's have over twice as much onboard max sequencing memory as the MPC 
(300,000 compared to 120,000 events). BUT, the MPC has the easy access disk 
storage, where as the xx7's have all of the patterns internal when you start 
it, which wouldnt be bad if it weren't such a pain to have to use the one 
part of your studio that you dont want to take to a gig with you (the PC) in 
order to load and backup the entire thing.

In the MPC's favor though, is it has twice as many simultaneous tracks that 
can be playing at once, BUT, on the other hand, the one I had been using had 
the newest OS, and still crashed 3 times as much as the xx7s.

If you want easy to use and sequence sampling capabilities, the MPC is 
great, but the xx7s have all the onboard sounds...so it just depends on how 
you prefer your source material.

The xx7's ALSO have all the assignable knobs, but if you have a Nord Modular 
(you didnt say which Nord you have) then you already have more than enough 
knobs I'm sure.

The MPC's pads are much nicer imho, and the roll button is much easier to 
use, and you can change the time signature in realtime as well, which the 
xx7s can not do while rolling. In fact, the xx7's can ONLY use the roll (or 
repeat) function while RECORDING! AH! That still pisses me off.

The last BIG difference is the external midi sequencing cpabilities....the 
MPC wins hands down. The xx7s do a good job, but are a bit tedious for 
configureing every single pattern while still retaing internal sound rom 
sequencing capabilities, which in themselves can be glitchy as well (in 
terms of the right patch STAYING saved with the right sequence!)

....geeze, sounds like I made the wrong choice! lol! jk, I'm happy with the 
xl7, but i cant honestly say that I wouldnt go the other route if I had the 
chance to. Overall, I found the MPCs more user friendly, but I also consider 
my K2500 user friendly, which many people would beg to differ with.

To sum it up, the MPC's are extremely well endowed drum machines, and the 
xx7's have the potential to blow them away in terms of capabilities and 
flexibility, they just have some things to fix in my opinion first.

At the top the answer to "use external sequencing or PC sequencing?" is a 
very complex issue and you will get lots of advice on that. Bottom line: 
the choice depends on how you like to work, how you like to interact with 
your gear, your tolerance for dealing with non-music issues, and your 
affinity to the screen-mouse-keyboard interface. 
 
I've used an MPC3000 for a while and am familiar with the MPC2K sequencing. 
You will find I believe that the MPC is a better work horse sequencer for 
studio work. You have many, many more tracks to work with (XX7 is only 16). 
You can have sequences of lengths of your choosing (the XX7 restricts 
patterns to 32 measures or less and its one song sequence is a tad on the 
underpowered side with its single, though multichannel track). You can also 
run two sequencing in parallel, which is a valuable tool in itself. 
 
The MPC way of working is pretty smooth and conducive to laying down tracks. 
So is the XX7. the XX7 has grid-style programming (Roland X0X style) where 
as the MPC does not. 
 
The MPC is a bit stronger at MIDI editing but the XX7 is improving in this 
area. 
 
The XX7 is stronger as an interactive or live performance tool. It also has 
those sixteen programmable knobs which can be useful (though in your case 
the Nord and SNII has that pretty well covered). 
 
Finally the MPC has storage options like floppy and SCSI drives. The XX7 
requires connection to a computer for loading and saving its memory. 
 
Sampling on the MPC for beats and loops; built-sounds on the XX7 that are 
very good and expandable with additional sound ROMs. 
 
That all said, you will find the XX7 will work well in your use. Emu is 
committed to improving the XX7 and has announced its intention to have a new 
OS available early next year. The MPC, on the other hand is what it is. 
Akai has moved on to the monumental and still unfinished MPC4000. 
 
In my mind it would be no contest if you were comparing a new XX7 to a new 
MPC because of the price difference. But getting either at the same 
price... Hard to pass up an MPC that cheap! 
 
One additional thought. The XX7 will translate well going forward into a 
world where you become more and more computer-centered in your production. 
It can be a good control surface for software sequencers and software 
instruments. the MPC offers no such benefit. 
 
 
drk