Alright here's some info that might help you out. I own a psp 3000 and once had a chance to play with psp GO. There are two major drawbacks with psp GO compared to psp 3000. ONE is small 3.8" screen. 3.8" to me is too small for a hand held game device. I'd rather use my phone instead. TWO is closely placed keys. After playing it for a while my wrists started to ache a bit. It's more like texting with two fingers rather than playing game. So I think, despite of it's sleek look and reduced weight, PSP GO comes with its own disadvantages. PSP 3000 on the other hand is very comfortable to hold and play.
The problem with both of these models is that they cannot be hacked properly. The last time i checked, PSP 3000 could be hacked but a lot of the users were complaining that the device was unstable afterward (device turning off automatically, screen flickers, etc

. If i'm not mistaken psp GO cannot be hacked at all (not sure about this though). If you want to use unpaid games the best solution would be to buy PSP 2000 and do a ROM upgrade. Or else you can buy a PSP 3000 and buy second hand games off ebay (that's what i'm doing). Hope this helps. Good Luck!!!