Thanks fellas.
Will, that's a good eye you have.

Part of the reason I use different belts is because I am always trying different ones to see if I like one better than the other.... but the other part is because I feel (from experience) that some are better than others for certain tasks.
I like the Blaze belts, but not as much as many folks seem to. Unless a guy is grinding ballz out with heavy pressure, they don't last anywhere near as long as they are reported to last. While it's really hard to see in my low quality video, during the hollow grind hogging, my KMG was running full tilt/ballz out and that's with a 6" drive wheel! Also, I was pushing pretty damn hard. That's why it's so noticeable when I pull the blade off the belt to check it... it almost looks like I'm jumping from a burn or something... but it's just me backing the blade away QUICKLY.
For that scenario, the Blaze works really nicely.
For flat grinding, I
can grind with it full tilt, but I
don't like to. I prefer to back the grinder down to 50-60% on the VFD, which is still fairly quick with the bigger drive wheel. But it seems really slow compared to 100%! I also don't like to push as hard while flat grinding, especially when the blade starts getting thin. In this case, the 3M 967F (yellow) is my preference.
The only reason I had the 3M 977 on the rotary platen is because one of the last times I ordered belts that is what was in stock for ceramic in 120X.
I haven't tried the 3M 984 yet, but it seems to be getting good reviews.
So to answer your question, I would pick the 3M 967 if I could only have one belt.
Currently,
my favorite belts are the 3M 967 for grinding, the Hermes Jflex (blue abrasive/yellow backing) for contours, and the Hermes 36X aluminum oxide for hogging off bulk handle material.