How is he different or better than Grossman?
Just based on my own very brief first-hand looks at him in Tri-City 2 years ago, as well as reading a lot of scouting reports, he's a much much much better outfielder than Grossman. Great reads, great jumps, not world-class speed but fast enough. And fearless. Seems to have a knack for making the highlight play. Very good arm, too, I believe.
Hitting-wise, probably less HR power. Might steal a few more bags but not his strong suit, percentage-wise, though he has at least 24 SBs in each season so far. And he'll probably have all the walks Grossman has, but far fewer strikeouts. Average-wise, hard to say until he gets to MLB.
Grossman minor league career: in 2,820 PA hit .274/.383/.395 with 396 BB, 625 K.
Aplin minor league career: in 1,452 PA has hit .281/.377/.410 with 191 BB, 172 K.