If this doesn't turn into a 'fan boy' thread, I'll eat my face
I'm lucky enough to own both, and have done for many years - a friend actually convinced me to try the 360, whilst I was a die hard PC gamer... never looked back
Anyway the perfect console (for me) would be this:
PS3 hardware generally - as in the lack of noise (my 360/all I've tried are too noisy), small footprint (no power brick), integrated components (no need to buy a wifi adapter), but I'd happily choose whichever has the better graphics and speed... though it's hard to choose this as there's such a minuscule difference in most games; depending on how sloppy the developer it is really. Though, I must say, having recently purchased Skyrim for my 360 as well, it seems to run/load much quicker than my PS3 - saves in about 1/3 of the time too!
360 software - the dashboard now looks mature, and not the childish blade system of old, it also updates quicker than my PS3 (smaller system updates I guess) and it generally looks nice and has all the features most of us need in easy to navigate menus. That's not to say I dislike XMB mind you, I have always liked its simplicity - though, there are far too many system settings; but I guess this harks to the fact the PS3 is considered more of a media server than the 360 (going by previous posts).
Love it or loathe it too, Xbox Live walks all over PSN, and this is coming from someone who loves a moan about paying for Live - but this side of PS3 just lets the whole console down imo. As a lazy couch sitting gamer, I lament some of the simplest things being so difficult/absent on the PS3 - party chat for example..... where is God's name is that feature!?! The guide button features of the Xbox are also so simple - message flashes up, you press guide and immediately get taken to the message - message flashes up on PS3, press Home, wait, scroll to the menu, select friend, select messages.... etc etc.
As I cannot have a single console above, I would have to keep my PS3 - as I have over 100 Blue Rays.
Edit: Oh, I completely forgot the who debate about the controllers! Frankly, they both work really well for me - but the sticks of the PS3 have always (and still do) feel more fluid for FPS. So.... Xbox controller, but with PS3 sticks