hah
i would say since i own one and a ps3 to pick whatever has the most games you would like to play
ps3 is great for games online and shooters although the adventure and really good RPG games have so much detail and are so big they may lag at some points (i am talking about assassins creed brotherhood it seriously does that)
psp however is great for rpgs minigames and tactical games also fighting games for both i forgot about those proof of this is kingdom hearts birth by sleep awsome graphics and if you want to stay right next to a electrical port constantly on charge you can play it with the graphics at 32 bit which has like 16 million plus with colours for awsome graphics and to prevent lag they have a little option to run the game at 333 hz instead of the normal 222 hz so it won't lag but it wastes a lot of battery
best one to get out of the psps is mainly the 2000, 3000 is great but 2000 is much easier to hack and you can keep it updated if you want
best amount for a sd card is to get at least 8 gigs of memory on it thats the least you will ever need if you don't mind deleting a few games every time you want a new one