Without encoders your mounts already guide up to the limit imposed by seeing. How much will encoders improve the results of guided imaging? No one is questioning whether encoder mounts track better or are superior for unguided imaging.
A test like this would be helpful:
- Have encoders on, calibrate PHD2, use default PHD2 settings, set a 3 second guide interval, run 200-400 samples .... check the total RMS error
- Turn encoders off, have PEM disabled, recalibrate PHD2, default PHD2 settings, 3 second guide interval, run 200-400 samples .... check the total RMS error
Repeat the test a few times and compare. It would be best to use optimal PHD2 settings with both encoders on and off. The above test would be simple and give at least some idea of the difference though.