SSO/FRO (Spindle Speed/Feed Rate Override)

[Neale]

Overthinking - now there's a man after my own heart

I would see two reasons for encoder over pot. I think that you've mentioned both. One is that at switch-on, if no other time, you can reset to 100% in software as the encoder is a relative rather than absolute device. No starting up at 200% because you didn't notice that the pot wasn't reset. Second point is about noise. Yes, you can filter low levels of induced noise, but my own experience is that it can be more problematic if the pot track itself is noisy. I built an Arduino-based temperature control for a soldering iron recently and suffer badly from this; I'll be changing to an encoder when I get time to do it. The software to support one or the other is pretty trivial. I suppose that another answer would be to buy a decent quality pot and not use the 30-year-old one that was already there, but I think that the first reason is enough in itself.

I can't make a call on other times that you might want to reset in software but switching on in a known, safe, state would swing it for me anyway.