Shields has shown he has great potential at gunner on punts and good potential at CB.
Bush is more ready NFL ready but doesn't seem to have a lot of potential, and he's usually in good position but QBs have throw right at him or right next to him with him in good coverage and he hasn't knocked it down and the WR got the ball.
I'll take the good potential guy over the looks good until the ball get near him guy (who also gets a lot of penalties).
Nether one can return so that shouldn't factor it other the coaches for keep putting one of them out there. That's on the coaches not the player, also there is a back WR who probably won't make the team that i read was very good at returns in college. I forget his name but if true I wonder why he hasn't been out there.