Just some comments:
You can upgrade the HD space on the PS3 yourself by replacing the drive with (almost) any 2,5'SATA drive. I've heard you can't on XBOX360.
The XBOX360 has probably more and better looking games because it has about one year lead time because it was released earlier, and by the way look at the first games for PS2 and compare them to e.g. God of War 2.
Online gaming for the PS3 is cost free, on XBOX you have to pay for it.
If you want to use you console as a cheap HD Video Player also it is relevant that the PS3 can play BlueRay out of the box. As HD Video playing devices will come down in price this feature will be less relevant in future though.
Now that the PS3 is somewhat comparable in price to the 360 we will see which will get more steam, especially when the big titles for the PS3 start to appear.