Graphically, this is not a port of the Nintendo DS. The screens provided from GameFaqs for the PSP and DS are not identical. Even though the PSP Screen shots may not be that good by PSP standards, they are certainly better than the DS Screen shots. I'm not saying which takes most advantage of their specific hardware, but they are certainly different.
You'd have to be quite blind to suggest that the PSP and DS versions are the same even "ports" for that matter. I have both and they look (and play) COMPLETELY different. The DS version has different menus, HUD, visuals (it looks closer to a very high quality PS One game), a track editor AND a paint/decal editor.
You can customize your cars as soon as you unlock them in the DS game (it does take a while, as it's a sort of MS Paint variation - simple to use). The DS version is also a bit easier in terms of handling - less slippy control than the PSP version, but not a complete cakewalk either.
The PSP game isn't a "4.0" score at all I say. The guy who wrote that review simply can't play the game or was too lazy/busy to put more time into it, period. In terms of handling, it's very slippery, yes, but it's also VERY much like WRC (the PSP version) or V-Rally 3 (PS2, Xbox, Game Cube) where if you go into the game expecting a super easy time, you'll flail and fail time and again. Then you get an almost Zen-like groove going and it's pretty much a very different experience.
Of course, It takes a LOT of practice and coming in 2nd or 3rd before you nail the tracks. Your fingers will be working the buttons and D-pad furiously (which works a bit better than the analog here) like a real rally driver on the pedals and shifter each race. You'll actually feel relieved when you finally start winning races and earning money.
One BIG tip: TURN THE MUSIC OFF!!! it really helps concentration when tunes aren't blaring away. Hell, how many real rally drivers play LOUD music while they race? Not that this is a sim, mind you, but still..
"You know, there's nothing but terrorists and military freaks down there." "Well, I won't be shaking hands and collecting business cards."