It depends what you’re using it for. I have a simple 40gb PS3, and it works fine for me. I pretty much only play games on it (very little internet downloading/usage, and no movies are stored on it… I have a computer for that nonsense). They are right that many PS3 games will store regularly needed info on the hard drive, but I’ve not even come close to filling mine.
Also if you plan on pulling out old playstation 1 and 2 games for nostalgia’s sake (as I did) keep in mind the lower memory ones won’t play certain ps1 games or ps2 games. Mine for instance will not play any PS2 games (that I’ve tried anyways), but has no issues playing PS1 games (again, any that I’ve tried anyways). Thankfully I still have my old PS2 on hand to fill that urge.
Have fun, and hopefully you never use xbox again, I know I never will.