1. I've been wondering the same thing about Fallout3 myself, on the fence about which version i'm going to get (360 vs ps3) As far as i can tell the PS3 version has 1 or 2 additional bugs, over the other versions which have bugs as well, so I think alot of the Inferior on PS3 stuff is overblown.
2. Well for PS3 right now If you're an RPG fan i'd recomend Folklore - you may be able to find it for cheap if you look hard enough. Most of the PS3 RPGs will be more JRPG like. Valkaria Chronicles is a SRPG that's getting very good scores, the game is very polished. Next year White Knight chronicles is coming, which will be a big game from level 5 - It has an extensive online mode that is supposed to be mmo-ish like monster hunter.
3. MMOs, I think 360 has phantasy star online and FFXI(both of which you can play on PS3 if you have a BC compatible PS3.) As far as MMOs are considered, Sony has alot of them coming in the future for PS3, but who knows when they'll arive. All of SOE's projects (DC universe, The Agency, Free Realms and whatever comes next) will show up on PS3(and not 360) as well as PC. The FinalFantasy XI team is working on a next-gen MMO that has been in development for a long time that will be on consoles. And Sony also contracted with NC-Soft to bring some new MMO projects exclusive to PS3. I think MMO's have a long history of drying up and never to be seen again, because of the huge investment required and extensive online structure necessary, so it's hard to count on them ever making it. 360 is supposed to be getting Age of Conan, huxley (both of which i wouldn't count on to show up on 360 as developers have made it clear 360 is a second priority) and APB (could be considered an mmo).
4. As far as online play on PS3, It's popular enough to find a game just about anytime on any game, You may have trouble during really late hours on obscure psn games though. I just went on UT3 and had no problems.
5. Install times, really can be frustrating, MGS4 is the only game where you have multiple times you have to install. I just usually go make a sandwhich, bathroom break or read the manual. About half the games from 3rd parties have installs now, but doesn't bug me all that much.
