I do not know much of the financial end of the X6. However, i have driven both the 35 and the 50. I am a huge fan of the 50 over the 35, even if you cannot dish out the money for a brand new one, there are some great deals on 50s with less than 10k on the clock.
The roar of that engine is unbelievable, and the way that it corners is great. I am personally a fan on the Alpine White..
BMW : X6:eBay Motors (item 150386813939 end time Nov-27-09 12:33:10 PST)