I think Stokes has a lot more potential than Woakes, so is probably the right call. Buttler will be knocking on the door soon, especially if Prior's form doesn't pick up.
I think Stoakes has a lot more natural talent than Woakes. His bowling has improved a lot already and he can get up to good pace and reverse swing it and his batting can be very destructive.
Long term woakes is a 6 who bats well and offers something with the ball if we need it and Stokes is an 8 who is there for his bowling but does the Bresnan job of scoring important runs in the tail.