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I have a feathertouch 10:1 manual focus on my 9.25 SCT - for rough / quick adjustment (haven't touched this in a year or more), at the back of this SCT is a Meade motofocuser (controlled via a JMI USB box by PC normally running BYE for imaging control). The Lumicon OAG hangs off the Meade motor focuser then it all connects to a cooled DSLR.
Side by side with this I have two Williams Optics refractors - the larger one is a 110 FLT triplet that uses a Moonlight high precision encoder focuser with both fine tocus hand controls and USB override to again let another instance of BYE (or any other suitable program) manage precision focusing of the second DSLR.
It's just by casual observation that I say the Moonlight looks way higher build quality and capable of rigidity under fair load than the older Meade. I have never tested them, and the Moonlight I believe costs double or triple what the Meade did. Mechanically I haven't tried to evaluate (even mentally) which design should work better. When you consider the tolerances needed, and that all metals flex under load, you might have to think through thoroughly how all surfaces are supported and their strength, length and the turning moments associated with their designs before assuming rack and pinion has direct contact so will be more stable. Good question thought.
One lesson astro-imaging has taught me is start from the assumption that all metals bend under load like plastic under a hot sun, and ask is your gear set up in such a way for this not to be an issue for you! I used to assume its steel its strong, those attachment points must be enough etc. One semi loose attachment point can be a PITA to identify and correct if you don't get a bit paranoid at the start about unwanted flexure!
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