I suspect the Xbox 360 version will probably be better than the PS3 version too. I say that and I intend to buy a PS3 during my summer break.
It is well known amongst the games developing community that the more powerful, yet different architecture of the PS3 makes game developing/porting quite challenging.
For example, Colin McCrae Dirt was delayed 2 or 3 months on the PS3 as they tried to use the extra power of the machine. Turned out, the differences were hardly noticeable, so makes you wonder if they tried, found it too difficult then just gave up.
Xbox 360 cross platform games are likely to continue to be better till at least the end of the year until programmers learn how to untap the immense power of the PS3 (which has been discussed on previous threads). PS3's now outsale Xbox 360's and with Blu-ray winning the format war this trend is likely to swing even more in favour of PS3. Microsoft dropping the price of their console is a practically an admission of defeat.
I think programmers realise that the future is looking very 'black' with a silver four letter word on it.
I think by early 2009 we will see the ps3 versions of cross platform games being significantly better than Xbox 360.