I can't make up my mind which one I want. Anyone have a pro/con list of both?
What are YOU looking for? What do you want out of/in a ROM? That will determine the best one for you.
Steel Droid is more Blur/Stock Based. Liberty is more AOSP. Liberty has more customizations. Steel Droid has better battery life (according to most)
There are also several other ROMs out there. Maverick (currently on my phone), Eclipse, BioWeapon X, Rubix, Hashcode's ICS. That's not even all of them.
I would read through each ROMs description and decided what you want most.... or just start flashing til you find one you (and your phone) likes ;-)