I just got my unpainted Revised Core Set in today. The "Hans" in the Premium set uses the same legs as the earlier light walkers, but the one in the unpainted set has these same legs mounted side by side. I like both sculpts, and it does add a good variation to my light mechs. I have 2 more Revised Core Sets due here on the 14th, and will post pics to see if the legs are the same in them all of if my unpainted set is a fluke. I am hoping they are the side by side mounts, as I will switch them out on my earlier lights to give some more variation. Right now they all look the same.
I did not notice any other significant differences. The pose on one of the Heavy Laser Grenadiers is actually better than the painted one.