Stokes' numbers are way better than Curran's. In tests, he has more wickets per game at a better average, and he has scored more than 50% more runs per game at a 50% higher average. In ODIs, Stokes' numbers reflect what he is, a batting allrounder - his batting numbers are very strong. Curran has the batting numbers of a bowling allrounder and bowling numbers of a batting allrounder in every format except T20I, in which he has the numbers of a bowling specialist.
wrt striking at the right time, I did a bit of a dive into Curran's test numbers a while back because commentators kept saying that he had the 'knack' of taking important wickets. He doesn't. His wickets are evenly distributed between top and lower order. If anything there is a bias towards taking the lower order.