Right now 360 has broader library but it clearly still does have reliability issues and if you plan on being online you need to consider paying for MS service vs Sony's service being free.
On flip side PS3 is without question more reliable product but it has weaker library overall (although i suspect this will cease to be the case by end of year or early 2009 at latest). PS3 does get you BR if that is of interest.
I'd say have a good long look at what exclusives are known for each for at least next 12 months - i.e. 360 will have Fable and LO but PS3 will have FF plus GT5 & MGS and White Knight Story (I think that's the title) - and see which titles appeals most to you.
Multi-platform titles (of quality) are essentially the same on each now (despite pixel pouring fanboys). If you look at DMC4 or Asssassins' Creed or Burnout Paradise (or GTA IV) on a typical setup then to the average joe they look and play the same.
If I was to consider a 'tilt' approach I'd probably suggest the PS3 might be better for you as in the long run I think its more likely it will end up with a more diverse library (particularly outside of shooters) than 360 - but of course that's just my own feeling.
Or you could get a PC!
Try to be reasonable... its easier than you think...
