Which ThinkPad should I buy to replace my MacBook Air?

AB wants a new laptop for his studies and has narrowed the choice to two Lenovo ThinkPads. Which would suit him best?

I enter grad school this fall, and plan to upgrade my 2015 MacBook Air. After a lot of research, I've narrowed it down to the ThinkPad T480 and the sixth-generation ThinkPad X1 Carbon. With modifications and warranties, both fall within my a1,800 (1,599) budget, with the T480 being marginally cheaper. However, being a student, portability is a major priority. The X1 is certainly lighter at about 1.2kg, but how much of a difference will this make in practical terms?

Keyboard quality is another prerequisite, with reviews proving inconclusive. Which device would be a better bet?

These two 14in laptops should not be comparable, because they are based on completely different design philosophies. It's a testament to the progress made in reducing the size and weight of traditional laptops that they are now surprisingly close.