IMO I got a bit more enjoyment out of my PSP then my DS. Only reason was because I had homebrewed it, and it had failed during the homebrew. The battery basically broke and could not keep my PSP on. I enjoyed it when it did work, but honestly you may want to go with the DS if you're not going for Movies and Music.
The DS has touch capabilities so you basically get a lot more interactivity right there, which is a plus imo. The DS has a better selection of games (imo), and if you like Mario and stuff this is your handheld console. What makes or breaks a console is the first games you get for it, this is true as it makes you wonder if all the other games will be like it. My first game for the DS was Pokemon Pearl, and it was fun, so I enjoyed it. I believe the DS may be a better choice for you, as the games seem to be cheaper then the PSPs game selection, the console is greatly cheaper, and it comes in a variety of awesome colors. The battery lasts longer, and if you're looking for something that is for fun, then I reccomend this.
I will now say something negative about the PSP, the PSP's battery is craptastic. Only gives you a few hours of gameplay on it, which can really break the console. You are close to beating a mission or doing something really hard then it dies. You're like wtf? It was the battery. I also feel that the PSP has a clunkier feel to it, it's weird looking and just feels kind of ehh. The analog stick is terrible imo.
I feel that the DS may be a lot better for you in general. If you're looking for a handheld console that can game, this is for you. If you're looking for a multimedia system with a bad battery and clunky feel then the PSP is for you. Nintendo has and always will be a great company. This generation they may have felt like they abandoned the true gamers, I don't believe this is the case, as they have given us some pretty good titles. I believe Nintendo is doing the right thing and getting more people to enjoy their products, and I am sticking with them to the end.
I will reccomend you the following games, as you're starters if you do decide to buy the DS console by itself.
New Super Mario Bros
Pokemon Diamond
Nintendogs (I wanted this game so bad, never played it.)
The Legend of Zelda: Phantom Hourglass(never played really)
Animal Crossing: Wild World
I don't really know what you're into, but I can give a quick summary of each game which I believe may be true.
New Super Mario Bros.- A game which has updated the graphics from the original Super Mario Bros., but has left the fun and awesome gameplay alive. Indeed worth picking up, there is local multiplayer which I found enjoyable, if you know someone with a DS as well.
Pokemon Diamond- Another pokemon game, however this time with online multiplayer, and trading! This will make the game even more better, as it finally becomes competitive with others, and you can trade pokemon with people online. This game is really fun, as is most pokemon games.
Nintendogs- From what I've seen of this game, it is a game where you get to adopt a dog/s, and play with them, and enter them into competitions. It looks really good, as you can train to them to do tricks and stuff, as well as other things.
The Legend of Zelda: Phantom Hourglass- I haven't seen to much of this game, but what I can tell from it so far is, it's another Zelda game except with Puzzles, in which you use the DS touch screen to solve. Sounds pretty good, may pick it up later, if it ever drops down in price.
Animal Crossing: Wild World- Ahh another fun excellent game, if you've ever played the original Animal Crossing for the GC, then this game may be for you, if you've enjoyed the one for the GC. I personally couldn't find this game to entertaining, but that's probably because my brother kept stealing my DS to play this, lol.
And there you go, my final verdict is: Get a DS and get to playing some epic gamez!