I like to mess with the mods that fans put out so it gets a lot of longevity there. So, that's a vote for long game life on PC.
I also like parking my arse on the couch with my feet up on the coffee table, so playing on 360 is also a huge advantage for comfort, heh.
PS3.... I dunno. Don't owned one and honestly never played a game on one. Hell, I don't even know if I know where the power button is on one, heh.
I am not aware of any computer eating DRM on the PC version. Copy protection is probably not much different than Oblivion's was, though I wouldn't quote me on that. I think I have read some previews already that stated that, compared to other games out there that ran people through the gauntlet of DRMs, Fallout3 was a happy medium in comparison. Don't think I would worry there.
Sadly, it looks like a 360 version slipped the cracks too. I don't know the whole story, but my only guess would be that a press-reviewer's copy fell into loose hands and they managed to strip it and torrent it. So folks with the know-how are dl'ing an ISO and slapping it on disk to play on their modded 360 (I think the word was that it had to be modded, not 100% sure). regardless, and this is s funny story, yesterday, someone was playing it and realtime streaming. A couple of us were watching it online here and wouldnt ya know it.... the numbnut opened his dash blade and BOOYAH, we got his Live name, hahahaha. The intelligence level of petty crooks just isn't as romantic as it used to be.
Ya, I'll keep my ears open for copies and prices in hopes of putting a group buy together. Been getting harder to do lately, but it's always worth a try.