I had doe tags for 21, it took 3 days to kill a doe on public land. Plenty of public ground, but the southern portion of the unit seemed void of animals. I never made it over to the Ed O Taylor area because the roads where horrible. I would suggest getting there opening day, only because we talked to 3 deer hunters who killed 3 antelope bucks on the second day of season...I guess everyone was still deer hunting. When we started looking for doe about 8 days into season they seemed to be all gone.
If you dont have points and you are looking for a fun hunt and your expectations are not high, then go for it...but just know it took me 3 days to kill a doe. I have killed 3 antelope bucks before, so I know a little about hunting them and 21 seemed to have enough public ground to keep you busy but the antelope were just not there (while we were looking for them).
20 has less land that is public, but we did see a couple bucks on the border of state land. Come to think of it we only seen a few dozen antelope in the southern portion of 20 period...including private.