This thread wasn't which one you would pick for just this season. There's every chance Sanchez has the better career.
Last year:
Sanchez = 3.9 WAR, 3.55 FIP and the AL leader in ERA (3.00);
Stroman = 3.6 WAR, 3.72 FIP, 4,37 ERA.
We should just be grateful that we've got two young controllable starters who when injury free can be borderline aces.