I can say I have had better success with load cells than dancers.
The dancer is essential when the egg shaped (core off center) rolls are used, particularly on unwinds. I heard one vendor from Asia ask “Why would you want to make egg shaped rolls?”.
Intuitively, the dancer makes sense because it will absorb tension disturbances.
Load cells are much simpler to control. The load cell measures tension and can easily be calibrated. Dancer regulators regulate position. Pressure controls the tension.
Practically, it is very difficult to design a good dancer. It should have low inertia, the pressure in the cylinders should remain steady, the cylinders should be free of stiction. The best performing dancer systems I have tuned had excellent mechanical engineering.
Please comment on your best and worst performing tension controls.