Should I get the PS3 60g or 80g version?

I am getting ready to buy a PS3, because my roommate is willing to buy my PS2 for $100. So I figure I might as well get a PS3. The local gamestop just told me the 60g is the way to go b/c you don't have to download anything for backwards compatibility, whereas the 80g model you have to jump online and do some downloads. So is the 80g model less b/c than the 60g? Even though I will get rid of my PS2, I still want to be able to play my old PS1 and PS2 games likeMGS3 and Fatal Fury Anthology. Just trying to save space in the house. Also, canyou still play online with with old PS2 games with say Killzone 1 on a PS3. Thanks for any help.

I would definetly get the 60GB because im pretty sure that the 80gig isnt backwards compatibile with all ps2 games. Sorry but im not sure about the online question though.