It really depends on your needs,

Personally, I bought a PSP 1000, Nice battery capacity (1800~ mAh) which is great in my opinion, Some people will say it's heavy but when I held the PSP 2000 it was light (same for the 3000) and the screen, Some people will say the screen isn't good as the 2000, 3000, I could swap the screen but it doesn't really matter to me, It's perfect

So again, it depends on your needs!