The only difference I know of is, the trigger housing on the older rifles use a steel trigger housing, where as the new one's are plastic.
The older trigger housing was cast aluminum with a black painted finish that would flake off with age. The new plastic part is tougher, stronger and has no paint to flake off.
If you go back to the very early guns you will find a bit better quality of finish on both metal and wood. The newer guns are far more accurate in my experience. This change is very recent. The 2 guns I bought for my kids less than 10 years ago are not even close to the newer 10-22's I've bought and shot. Starting about the time they changed over to the plastic trigger group Ruger's started to improve their accuracy. My newest 10-22's shoot right with my CZ.