Having owned both, I can say that the D-pad AND buttons are both raised a lot, making it control just like the pS2 controller.
As for the brightness, it depends on which model of black you own. I compared mine with a bunch at GS and found that some were much dimmer than the white PSP, others were just slightly dimmer.
you can't play region 1 UMDs.
I personally think the raised buttons make it worth the extra dough. I can't ever play a black one again...it just sucks horribly (no offense to people who own them.) Then again, I'm a big fighting game fan, so I might be a bit more sensitive to these kinds of things.