Dan not only confirmed that the Xbox 360 does limit what they can do with the game, but also suggested that the PS3 also has a few limitations of its own.
You can definitely count on Rockstar doing a great job with the game for both platforms, but which version, if any, will end up being a "better" buy? This question is probably only relevant if either you own both consoles, or if you don't own any and are still deciding which one to buy. The Xbox 360 seems to have greater limitations without it having a guaranteed hard drive, and the fact it uses standard DVD's, but then again, it also has exclusive content confirmed for it, while the PS3 version doesn't.
On PS3 you've got a guarantee that every machine is going to have a hard drive and, with Blu-ray, you've got plenty of storage, whereas on Xbox 360 there's no guarantee of a hard drive and you're working with the DVD format. Does that create limitations?
"Yep. To be honest with you we haven't solved all those riddles yet. Both of them have enormous challenges. Again, that's been an advantage having the guys at San Diego who are freakishly clever and full-time dedicated to us, but we're not there with either yet. There are problems on both. We'll get there with both, but both have their own particular pleasures and pains."
It's not clear what the specific limitations are for the PS3 version, but hopefully whatever they are they will be sorted out before October, the same goes for the 360 version. We'll update you when we get further information on the differences between both versions of the game.