I prefer the Hougen "RotaCut" cutters
kit number 11075C and order an extra couple of the smallest two cutters.
I've cut hundreds and hundreds if not thousands of spotwelds with them. I would resharpen them on the belt sander occasionally. They only die when you catch one tooth to many times and break it off, but can still last a while longer missing one.
Looks like they have a size or two even smaller than the kit comes with, I may order a couple of those for the little bitty spot welds.
I've used the Blair ones, but they don't seem to last as long.
Grigg