major differences

The D1H is pretty only and only 2.1 mp which is pretty useless if you expect anything to be run in a mag. its also very old like 7 or 8 years old, old technology, slow, only shoots 5 fps, its a waste of money,
the d2h is like 4 or 5 years old and is double the Mp 4.2, 8fps, better build,.alot of pro photogs i know shoot with a d2h for sequences, you can still get useable stills too, i've had full page shots run with my OG 1D which has the same resolution as the d2h.
The D1H isn't even worth the bother.
if you don't want to spend the money on a d2h get a used D70 or D50 both sync with flashes at 1/500 (d70 snyc is pushable to 1/1000). or even look at a 200.
anyways thats just my 2 cents.