Please do not rely on any of them for glucose decisions. They are not reliable at all.
Finger sticks or CGM (Continuous Glucose Monitors) is the way to go.

Are you talking about using a wrist monitor for Blood Glucose testing??? If so, I didin't know there was such a monitor. I do have one for Blood Pressure and I do compare it with my doctor's reading when I am at the office and they are nearly the same and have gotten an approval from my doctor to use that for my daily readings.