The Carbon X1 6G is 120 grams lighter and has much more ports. Gonna leave Apple for good. The MacBook Air was an amazing machine for the past 8 years, but Apple lost its way. Too many cargo cults (slimness, few ports, radical changes, secretiveness, to name a few) and too little closeness to their customers (poor repairability, high prices, unwanted features).
I just priced out the Carbon X1 with similar CPU/RAM/SSD and it costs $1331 (vs $1399) -- plus the Lenovo has a slightly larger screen with lower weight and normal USB ports. I don't think it moves the needle for Mac fans, but it definitely moves the needle for people who are ambivalent between the two.
Not sure the specs you're looking at, but Costco had a deal on the X1 with 16 GB RAM + 512 GB SSD for $1399 earlier in the month, and I think it's $1499 now