Ok, so your thinking of buying a next gen system. Id say 360, the online experience is alot better on the 360 and I'd say the 360 has the software to back it. As for reliability issues, the 360 has gone through various changes over the year or 2 its been out, I think its on its 3rd hardware revision right now (falcon) which is alot less RROD prone. But still MS has got you covered for 3 year incase your stupid enough to leave you console in a non ventilated warm place, it should go with out saying not to do that with any console.
that aside, when you look at the ps3... it doesnt have the software or online advantage. But it does a slight have an edge on the hardware but its really just the processor. but even that isnt as easy to take advantage of as the 360 due to its better dev kit. The GPUs in each are relativly similar performing. However the memory I'd say in the 360 is better implemented, the ps3 has 256mb dedicated to graphics and 256 dedicated for processing / general purpose tasks While the 360 has 512 mb or ram that doesnt have just 1 dedicated tast, in some cases the 360 could have more video memory or more general pourpose memory.
Over all I'd go with the 360, buying a system just based on hardware is a horrible idea. Ask your self what brings you enjoyment when using a game console? when you turn it on do you say "wow this game kicks ass!!!" or "wow I bet I could process alot of information with this". Its the games that make a console and at the moment I think the 360 has the edge.