I don't think you should compare a handheld to a home system. It's not like your getting the same experience. You should be happy with a DS but it just isn't the same as having an expensive home system with surround sound and the like.

Both the 360 and PS3's libraries are really just the same at this point. Microsoft chooses to just steal exclusives from Sony than expand the market with its own titles so has made decision making for a console extremely hard at this point. Sony has the right idea with its first party line-up and if you look ahead into 2009-10 its clear that the PS3 dominates. But then again Microsoft always has tricks up its sleeves so they won't leave 360 owners out in the cold.

I think its also important that you own a HDTV if you plan to buy a PS3. The PS3's entertainment value increases ten fold if you do have one. Firstly you don't want a blu-ray player lying around doing nothing. And secondly, and more importantly, Sony encourage their developers to always develop with HD in mind so a lot of PS3 games look crap on SDTV's as the system has problem aliasing to that resolution. So when you compare some games on the PS3 and 360, the PS3 games look worse than the 360 version when on SDTV's but better on HDTV's. Its a pretty big issue and one that doesn't really get mentioned. I noticed it the other day when I misplaced my HDMI cable and played Wipeout HD through my scart socket. Small text is unreadable and it just looks much much worse.