MDA from Tmobile Germany, this one would have to be flashed with an English Rom. (some places are doing it. - question to ask does it have English manuals or German ones) You would void any warranty and you are stuck for any upgrades. I personally would not buy a GERMAN ROM.
Imate - Great deivce, English original ROM. I have one, works well, official updates, worldwide warranty. Great tech support.
XDAII - O2 you might have to unlock it but with the new tool no problems. I would have no problems buying one.
I do not think you will have any performace issues. Just slight changes in add on software for each device.
Personally I would go for a Imate or XDAII. I would not spend all that money on a hacked MDA.