I daily a T480 with Debian for work, and I’d recommend it highly. Great performance, battery, build quality, look & feel, etc. We have some 7480s deployed and while they’ve been solid as well, I much prefer the thinkpad. T series will have better performance and battery than X series, also, so I’d take the T480 over the X1C.

I now realize you are trying to buy a laptop on a budget. I’d definitely go for the X1 gen 7 or 8, 16gb of ram minimum. The 1080p screen will give you better battery life but the 4k screen has Dolby vision and will make watching movies a better experience.

What are the apps that you will be using? I’m really excited by these new Qualcomm laptops coming out. LTT is doing an experiment and having 3 of its employees switch full time to see if they are viable. If you can wait another week I’d see what their conclusions are.