I think one of the biggest advantages is backwards compatibility with PS2 games, but beyond that I'm not really aware of exactly what you get. I was hard pressed to get the 60GB over the 40GB on release date, but it was 100 bucks, so not to bad.
Doesn't the 80GB model include a game or movie as well now? If you like the game, then the extra space and game may make it worth it to you.