The best barometric, physical prowess comparison I can think of is this guy:
http://www.nfl.com/player/dantehall/2504165/careerstats
If you compare Hall's apex on offense in 2003, you'll find them nearly identical to Austin's rookie year stats. 40 catches. 10 ypc. So Hall's offensive ceiling is Austin's floor. Obviously, Austin may have more WR skill and craftsmanship, so there is obvious room to grow. That told, they have similar physical dimensions.
Hall was the "Human Joystick" and rarely took a hit. Phenomenally fast and elusive but not physical or a tackle breaker.