What is funny is people say MP3 looks/run better because it's linear. But have you ever tried skipping a cutscene in MP3? Don't bother, you can't. Well you can once it stops loading but 90% of the time the whole cutscene plays out by the time the freakin' thing loads.
I literally didn't do the collectibles solely for that reason.
And guess what you can do in GTAIV? Instantly skip cutscenes and jump back into the game (alright bit of a black 'loading' screen but not long by any means!).
I'll be getting it on PS3 because controller. Multi disc won't factor in because they'll probably do it like HALO where you install 1-2 discs on the HDD and then play from the main one (good luck arcade 360 owners!).