Well the PSP has a larger screen and is fairly brighter. Unit is pretty smooth, not heavy by any means. If you're used to a SNES pad +1 poorly cramp making placed analog disc you'll be cozy on it. I for one want the thing but not for awhile. The current hardware has a few flaws such as a Square button that gets stuck, umds that pop out semi-easily, and Sony will not warrant a screen if it doesn't have over 6 burnt pixels. All that combined with a $250 tag and console priced games I'm going to wait a few years at this rate. Once it's fixed and the prices start to drop then I'll re-evaluate it.
As far as the DS goes, got a 1yr warranty where they'll swap it out so I'm happy there as who knows if the screen will get stylus raped. Unit costs $150, games are what GBA was priced which is sweet. I like the new gaming choices on it for control that Wario Ware and Feel the Magic bleed, but so does the sport stuff too (tiger allows you to slash screen like a club for swings, and madden you can touch moves and manually move players on the fly.) The upcoming Need for Speed U2 will have NOS booster control, mappable courses, drawing of car decals, etc which is nice too.
I'm in favor on the DS so far, just it sucks it has a 2mo dry spell as they forced the bitch out for Christmas (which worked in their favor then, not now with hardcore players - casuals will never notice the gap.) March has 4-6 games coming such as NFSU2, Pokemon Dash, Yoshi's Touch N Go, Bomberman, Rayman, and more. So that will be fixed -- just need to get their online shit in gear.
As far as NOW out recommendations since i saw that post there of being bored.
-Wario Ware (180+ games in it w/shitload of unlockables)
-Tiger Woods Golf
-Zookeeper (if you can find it less than overpriced $40)
Upcoming in March I'd nab NFSU2, Rayman, Bomberman for sure, and probably Yoshi's Touch n' Go. Game wise things will be 'fixed' in a matter of a couple weeks.