It's not just his pace, Schmelzer had pace, durm has the skill to operate contribute to our possession high up the pitch with more than just wild crosses. There's still work to be done but with how well he contributed when we had the ball, he was more than fine enough against it had our midfield been a little less abandoned.
Why Durm? Because the voting of the DFB can easily be manipulated - of a group of fanboys or even of one persons alone. You do not need to give an email adress or anything - just vote. And if the cache is emptied you can vote again. Reus was not second either - I thought he was even underwhelming to that what he can do. There is matches in which many players could get it - but at Sunday it should not have been a question.
Personally I think Durm makes our attack more predictable than Schmelzer. He always cuts inside to his right foot and when we also have a right footed winger on that side doing the same thing it crowds the space and makes it easier to defend attacks down the left wing. Offensively Schmelzer added a lot more than just pace and crosses. He makes very smart forward runs that pull defenders out of position. Its the thing that most impresses me about him actually. His intelligent forward runs are way underrated here.