Tru Grit is a real abrasive supplier for industry. They have a huge selection and which allows you to try various belts. Currently I like Cubitron II 948 in 40 grit, 120 grit. Cubitron II 947a in 120 grit. The price is higher but so it the efficiency.
VSM in 36, 50, 100 grit
Hermes 346 220,400
Gators A100, A65, A45
Cork belt in 220, 400, 1000
I use Norax structured adhesive belts for sharpening from 100, 240, 400,
You get more use from the Cubitron and Gators so you need less of them. The VSM, Merit cut well and as soon as you feel it is not cutting as aggresive as it should throw them away and grab another, the price is low enough to not mess around with trying to use them past when you should.
When the Cubitron stop cutting well, take piece of steel (hardened is better) and press hard into the belt while running. It is design to fracture the abrasive and give you a new cutting surface.
With Gators they like to wear unevenly and when they start to decrease their cutting I take a 50grit ceramic piece of belt glued to a board and run the gator while using the board on the contact wheel to resurface the Gator to flat and new cutting surface. This allow a very long use of the gator belts.
Good luck
