Honestly would give the baserunning edge to Wiemer as well. Frelick hasn't been nearly as good as Wiemer stealing bases in the minors.
Wiemer has played 236 games and has 61 SB to 9 CS (87% success rate at .26 steals per game). Frelick has played 154 games and has 36 SB to 10 CS (78% success rate at .23 steals per game).