The x250 can also take up to 16gb ram, at least in most CPU configurations. Some models (the i3 at least) cannot.

Many people like the x220 best, because it has the old-style keyboard (does the x230 as well?). The x250 has surprisingly similar performance but much better battery life.

Which is better? I don't know, but I bought a x250 back in 2015 and am still using it as my personal laptop. It only sees light duty these days.