What are the differences between the two versions of Ps3?

Sorry for such a dumb question , but I havent been around much but I plan to purchase a PlayStation (the 40g or 80g)

Also, is there backwards compatibility with Ps2 games and Ps1?

There is a lot of difference in the two systems.

The 40 gig has no card readers and only two USB ports. There is no PS2 game support and there is no update or anything else to allow PS2 games to work.

The 80 gig has card readers and four USB ports. It also supports most of the PS2 games (could be around 90% or more by now).

So if I dont get the 80g I cant play any of the Ps2 games (which I own a lot of)?.

I guess Ill wait until there is another option for now. Thanks for the help though.