Hello. I'm in exactly the same boat. Here is what I've kinda heard so far:
1. The Rubicon will hold it's value much better. Also, the upgrades are under warrenty. If you buy an X and start changing stuff, you will run a great chance of voiding the warrenty.
2. You can make an X as good or better than a Rubicon for cheaper than the Rubicon costs. Plus you are only changing what you want to change, as opposed to what Jeep thinks you want to change. Do your really need all of the stuff that comes with Rubicon? (I know I don't).
What it really boils down to is, what do you want? If your going to put a lift and tires only on the Jeep, using it only once in a while off road, an X would be the way to go. Why pay the premium for the upgraded Rubicon wheels (for example) only to replace them with bigger ones? If you are going to leave it mostly stock and are interested in the resale value, I would go Rubicon. If you are a hardcore offroader, rock climbing etc., the Rubicon is much better "out of the box" because of the sway bar disconnect, lockers, and 4.1 transfercase.
Also, try a google search for used Jeeps, comparing Rubicon to X, and you will see a large difference in prices.
I wish that the X could be had with the Dana 44 axel in the front, 4.10 gears, and the lockers, that's what I like the most about the Rubicon. I'm going to talk to the boys at Jeep this afternoon, I can give you their take on it tomorrow if you like. Of course this is all just my .02 and I'm no expert.
One other thing. You can get an 08 for about the same price as an 07 right now. I see no reason to even look at an 07 unless you are looking at used.