Firstly, if you get a Xbox360 for christmas, you'll have probably have had the red rings of death by New Year. Xbox 360's have a 33% failure rate, to be honest, that's a disgrace from Microsoft.
No games for PS3, eh? Here's some exclusives to be going along with:
MGS4
Gran Turismo 5
Uncharted: Drake's Fortune
Warhawk
Resistance: Fall Of Man
Haze
Eye Of Judgement
Ratchet and Clank: Tools of Destruction
Motorstorm
Little Big Planet
They're just exclusive games, there are multi-platform games that are out like COD4 and future ones like GTA4.
Also, HOME, which should be out in the Spring, it's going to be a free download from the PSN I think. Its like Second Life in a way that you have your own character and flat. For more info click the link below.
http://en.wikipedia.org/wiki/PlayStation_Home
Now, on to Disc formats, Blu-ray, which is the format used on PS3 discs, has a large amount of memory stored on it, about 5 times the amount the Xbox DVD's have. Plus the PS3 upscales normal DVD's to near high definition standard with the latest firmware updates.
Now onto price, the 40GB PS3, which is the only version you're likely to find unless you can find a 60GB which is a rarity, only costs £280 from Play.com. I think the Xbox Elite is somewhere around that mark, so the price is not considerably different to that of the Xbot.
Then there's wireless internet, which is not available on the Xbox 360, unless you get the top model of it. Linked to that Xbox Live, which if you want to play games online with, you have to pay £40 a year, unlike the Playstation Network which is free. Give the PSN time to grow, it hasn't been going in the UK for a year yet!