What's the difference between X1 and X220, again? I really wish Lenovo would get its act together with its product lines, because it's nearly the only company

What's the difference between X1 and X220, again? I really wish Lenovo would get its act together with its product lines, because it's nearly the only company besides Apple that makes hardware I can love, but it really takes time to unpack the logic behind its product lines. The other company is Sony and it has similar problems.