The x220 is preorder only right now, and unless you are lazy/want to support libreboot, don't buy one that is pre flashed. Save yourself alot of money, buy a cheap thinkpad (or other laptop or mobo), and flash yourself.
Mostly all you need is external flashing device (raspi, beaglebone, ch341a etc) and soic clip. (x60 you can libreboot from cli on the actual device, no need for external flashers).
Libreboot has quite good documentation, and the people in #libreboot (freenode) are quite helpful if you have any issues. I would recommend libreboot simply because it is Free by default, and easier to flash in most cases.
If you own a device that can be corebooted, by all means go ahead, but nothing beats librebooted x200 imo.
Now I am just waiting for the people to come in and say libreboot is bad because it is no longer GNU project (even tho it is still Free software, same license etc), I use software based on the software itself, not any 'drama' behind the software, and I implore you to do the same.