Hardware Reliability alone the PS3 all day long but really I think they break even on everything else...though the PS3 will likely have a longer life cycle since Sony is known to constantly refine existing products where as so far the XBOX has only had changes that are mostly to fix faulty designs in the first place.
But I have heard that IF you have to have a PS3 repaired, the costs
are higher than the Xbox 360. This coming from a Best Buy Geek Squad critter.