Most if not all blade balancers are not much better than a nail driven into a stud on the wall so you can hang the blade by it’s center and see if the blade will balance.
Why? because the ones being offered are not “dynamic” …they are static balancers.
I know some of us are old enough to remember seeing our Daddy’s and Grandfathers have their tires balanced and the tire shop used a “bubble balancer” …and that was that. Then the public highways increased speed limits to 70 and the manual-steering cars we had would shimmy the steering wheel at 70.
One day, some enterprising fellow invented a balancer that would spin the wheel ON THE CAR… and to place the weights on the wheel…usually only on the outside.
Then one day they had balancers in the tire shop that spun them OFF the vehicle….and finally we began to see tires being properly balanced.
Until you can balance a mower blade While It Is Spinning…..at the Correct RPM….. there’s not much advantage to spending any more money than a “NAIL on the WALL”.
(I may write a Broadway Play and claim the Movie-Rights to it….. kinda like “Fiddler on the Roof”.)
[When I sharpen the blades I do not remove them from the spindles.I use a hand file,sharpen the edges which never seam to too dull.. I don't think it affects their balance.]