Note that the biggest issue with non Dayco pully's is not that they don't work, but that they are designed such that the stock dust cap won't work.
There is a note in the box with the Gates one that talks about blah..blah..blah this and that with new bearing technology not needing the dust cap.
But if you can source Dayco's, get them as then the dust cap will fit. I'm having trouble tracking them down in Minnesota. Stores by me all have gates.