Not OP, but I got the X1 Carbon, which was (at the time) their top-of-the-line Ultrabook and believed to be their most Linux-compatible laptop.
I had a number of issues with the Thinkpad that were all relatively minor in and of themselves, but overall, I ended up switching back to the XPS 13, and I plan on sticking with this line.
I'm on my third X1C. First-gen, 3rd then 5th generation. Never had an issue with Linux compatibility. The middle one had a malfunction with the voltage regulator, promptly fixed by Lenovo. Other than that, my opinion on the X1 Carbon is stellar. I'm wary of some of the newer models, but not of this one.
I had a number of issues with the Thinkpad that were all relatively minor in and of themselves, but overall, I ended up switching back to the XPS 13, and I plan on sticking with this line.