A 04 or 05 X5 benefit from significant upgrades including: variable valve timing, angle eyes, blue tooth and improved looks. If you want a X5, I would suggest getting a 05 or latter.

The E60 is a sedan it is smaller and lighter. The 525 does not have all wheel drive. I own a E61 and love it, but I also loved my X5. The fact that it is newer may make it better.