They all work on the same principle. The accuracy would depend on how good they calibrated the the scale units, quality of the spring, and how much play is in the hinge. I have the X-tools / Radon rebranded model and it seems ok, except you have to lubricate the spring. I added a drop of oil. I don't know how accurate is the calibration, but I just set the drive side rear spokes to the maximum tension on the spreadsheet (I think 140kg) where it feels really tight and there is a lot of spoke twist popping. However, the reading is off by +/-1 units if I measure with the tool either up, down, or horizontal due to the slight curvature of the spokes. I don't know if this is normal for all tools, or if it's because the spring in the hinge is weak (also I have 20" wheels so the curvature of the short spokes would be more pronounced).
I just use it as a reference to help me get a feeling for the tension. I still pluck the spokes with my fingernail and record the tone on a chart, along with spoke meter reading, which helps me to decide which groups of spokes to adjust to get the desired movement.
Last edited by tomtomtom123; 11-25-19 at 07:36 PM.