I would imagine that the X121e is significantly better than the X120e due to the 121's i3 processor. But if you're gonna spend close to $600 then I say just go with an X220 with i3. My wife has the X120e and I have an i5 X220 and I must say that the X220 is much better than the X120e in more ways than just a better processor. First, you get better battery options with the 9-cell battery and optional slice. Then you get a better keyboard, larger screen and optional IPS display (which I highly recommend). You also get an Expresscard slot for upgrades. My slot is taken by an Ake USB 3.0 adapter (which is AWESOME!). All this in a package that doesn't feel much heavier than the X120e.
Don't get me wrong though, I love my wifes X120e - and so does she. It's the perfect laptop/netbook for the low price!
Yes, the price points and hence product offerings are spaced differently in smaller and/or emerging markets versus in the United States of America. Any word on potential changes where we might see an x121 or better derivative soon?