Are MCTs better than SCTs for focusing, generally being longer & slower? Ditto traditional & also DK Cassegrains like Mewlons?
This is not strictly speaking a question that can be answered, since the question is not about optics but about mechanics. Some aspects of telescopes are dictated by the Gods of optics. It is they, for example, who have decided that the human eye really isn't going to be happy with magnifications high magnifications in excess of 0.5 mm exit pupil. The thing can be done, but not particularly well.
What you might say is that is that telescopes with excellent focusers go into the territory of <1 mm exit pupil armed and ready for the challenge.
A cheap SCT does not. The focus mechanism is inferior.
But wait there's more! You have a 4 inch apo closing in on 200x you are in the zone of focusing carefully. You are also in the zone of dimming out. The c8 with the lousy focuser is still at 1mm exit pupil. The image is brighter. It is beginning to be difficult to focus.
Another scope might have a more sophisticated focuser than an SCT. Hellsbells, SCTs used to have better focusers than SCTs! The white and blue Pacifica SCTs had a pulley system that moved the mirror with equal pressure from two sides.
One can do better. It's just that they choose not too.
So there's no reason a pricey Mak might not have a better focusing system. It's not the optics, it's the mechanical design. But the mechanical design has its optical consequences.
But wait there's more!
Seeing conditions generally cap out at 300x. 1.2x per mm in this case. Even 25" Newts are capped at 300x a lot of the time. If you get a long Cassegrain like the ten inch Aries f/15, you're looking at $15,000 new. A 7.5 mm ocular will deliver 500x. So you have all this magnification capability that you're only rarely going to use unless you are well heeled enough to have a place in the Canary Islands.
Consider in contrast a C14 f/11, cheap at the price, $5,000. It too will cap out at 300x in most seeing conditions. But it will be at .8x per mm of aperture. Guess which one has better depth of focus? The faster C14: which unlike its cousin the c8, will at 300x have more focus depth in reserve than a c8 at 200x.
So there's a lot of things you have to put together. I would not want an f/15 ten inch Mak; f/11 is more than enough for me thank you. And I like the light bucket. There are also Maks that are more along the lines of f/7, but at those short focal lengths they will have to widen the meniscus (increasing the dreaded central obstruction). If you increase the dreaded central obstruction you might as well get an SCT. (Mak users will disagree!) And you've reduced focal ratio, so you're reducing your depth of focus advantage which is why you wanted to look at this to begin with.
You can get a long refractor. Add $5,000 to your mount costs. Many of these will not fit in a Honda Accord. some will not readily fit in a minivan.
In sum it's very hard to outfox the Gods of Optics on these matters.
In the end I would not buy a scope on depth of focus criteria.