Mitchell is both a better baserunner and faster human? Wiemer isn't anything special running the bases.
These are their MLB SB/CS numbers and BsR numbers.
Mitchell - 44 G, 130 PA, 9 SB to 0 CS, 3.0 BsR
Wiemer - 131 G, 410 PA, 11 SB to 4 CS, 0.7 BsR
Mitchell is significantly better.