Hmm... Pretty risk free decision if you need a new phone and the contract gives you everything you want/need, the PS3 is surely just a bonus?
If you're not really arsed about gamerscore then go for it. Controllers aside, everything on and about the PS3 just 'feels' better quality, and you'll notice that dodgy ports aside, the visuals are crisper and cut scenes usually a lot less compressed so also better quality. Add in the fact that PSN is free & games can all be fit onto one disc and the contest should be stopped by the referee, however that's not the whole story. The horrific new dash aside, there's just something fundamentally 'better' about the 360 experience. Online play is loads better, as is party chat etc - but this is understandable at £40 a head, but also the way MS have everything tied together within your profile is way better than the PS3 offering. Also bear in mind you do have to install some ps3 games which seems to take even longer than the xbox install, and the system updates... Well, get a good book if you've got to wait for one of those bad boys - although im reliably informed they are a lot less frequent than they used to be - i only really use my ps3 for blu-ray (which you dont need) so i rarely check if an update is needed!
If i were new to gaming however, i'd probably go PS3 now, as i think everything weighed up it's the better package, they also have better and more exclusives now which is in stark contrast to the early days - check out not just MGS4 (which is awesome), but uncharted, little big planet, heavenly sword, ratchet & clank, heavy rain, god of war, killzone(?) and thats just from the top of my head!
The 160gb hard drive should be enough too, but remember with the PS3 that if it isn't, you can upgrade it yourself using any standard SATA notebook drive (you can get a monster 2tb 7200 drive for just over £100 which is way more than you'll ever need so scale that down to say 320gb and i dunno, maybe £40-50?).
Suppose my most prudent point was my very first one about the phone & contract itself!
(2 + 4 = Fish) / Sloth = Better