We've taken a quick look at the XPS vs X1 Carbon together.

 Advantage of the Dell XPS 13 (7390):

• 4K Touch screen support
• Smaller footprint, solid build
• Decent performance (6-Core model funs fast, though could get hotter) 

Advantage of the Lenovo X1 Carbon (7th Gen):

• Dolby HDR Display is gorgeous 
• Business-friendly features, more ports, webcam privacy shutter
• Very similar to the X1 Carbon 8th Gen, possibly better prices