The PSP, info please!

I was planning on getting a PSP (the 3000 model), perhaps. I saw a PSP model (not sure which one, but the color was black) in GameStop, brand-new for 160 dollars or so. I planned on buying it, but then I wikipedia'ed and noticed that they're releasing the PSP Go in October in the United States shortly.

So my questions to you guys, for PSP users:

1) Why did you pick PSP over DS (any DS versions)?
2) Can the PSP hold music, as in, can you listen to music on your PSP?
3) Do you download music with a fee? Or can you just transfer MP3 music files directly from your computer?
4) What's the memory and all that on a PSP? This way, I can know how much music I can put into a PSP.
5) Does it save games by memory, or do I have to get one of those memory sticks or whatever?
6) Can I download PS1 or PS2 games as well?
7) What about battery functionality? How long does it last when fully charged?
8) When buying a PSP, what does it come with? Is it a USB drive, headphones, a game, or what?

If anyone could answer as much as possible (I'd prefer indepth), I'd be grateful, thanks!

PS: Yes, I know I made a Zune vs iPod thread before, but that's how I collect info. x) I'm getting a Zune 'if' the PSP can't hold too much music.

Also planning on getting Tales of the World: Radiant Mythology 1 and Tales of Eternia as SOON as I get my PSP!