1. Portability. One highly recommended beginner telescope is a 6-inch Dobsonian. The telescope weighs 25 lbs. The base weighs 35 lbs. On the other hand, my "grab-n-go" 4-inch refractor and its mount and tripod weigh 25 lbs combined. If you are a small person or you have mobility problems, the portability of a smaller telescope is important. The best telescope is the one that gets used.
2. Convenience. My 4-inch "grab-n-go" refractor was in for repairs and I enjoyed using a 5-inch Newtonian (Astronomers Withouth Borders). However, several nights, I wanted to go out, but had not planned on doing so and the telescope had not been collimated. I knew from experience that collimation needed to be set (or at least checked) each time. So, those nights I did not have the use of the nominally "better" telescope with more aperture. Also, just to say, at a local star party I helped one of our stalwarts collimate his 8-inch Dobsonian twice. It took two of us: one to view, one to turn the knobs. One person can do it alone: back and forth... back and forth... back and forth...
3. Choice of Aberrations. An achromatic refractor does have chromatic aberration. An apochromatic has much less (theoretically none, but theoretically also still a tiny bit). A Newtonian reflector has wires ("spider vanes") that create diffraction interference. Some people like the look of that so much that they photoshop spikes into all of their stars.
4. Actual aperture is the actual aperture. With a Newtonian, you have the central obstruction is which is usually given as 25%. (Some makes and models have more.) So, an 8-inch reflector is really a 6-inch aperture. So, the highly recommended 6-inch entry-level Newtonian is really a 4.5 inch entry-level telescope, just heavier to carry in two trips.
Those all being my reasons, the fact is that my first adult telescope was a Newtonian, a 130mm Celestron on an equatorial mount and I used it happily for five years and learned a lot about the sky. The best telescope is the one that gets used.
I am strictly a visual observer. (I have taken some snapshots with my cellphone.) Observing is my hands-on engagement in the hobby. My primary interest is in writing and I also volunteer as an editor. As much as I support other people's being "Citizen Scientists" I know that I am not. I do not track variable stars or look for comets. I am just a stargazer, as probably 90% of us here are. We are less engaged with celestial objects than birdwatrchers are with their feathered friends. Birdwatchers will put out feeding stations and hang housing from the trees and be mindful about keeping the cat indoors. We do nothing to help the stars. Even photographers contribute very little to science. (I know: there is a counter-argument from a Sky & Telescope article. but the fact remains that most astrophotography is just another kind of stargazing.)
You have me scratching my head.
1. The Orion XT-6 OTA weighs 11.9 lbs, the base 19.4 lbs. It's only 6 lbs heavier than your 4 inch refractor and equal in weight to my 4 inch apo on its mount.
2. Collimation is not a big deal.. it takes a couple of minutes once you know how.
3. Aberrations, chromatic aberration can be much more damaging than spider diffraction or a central obstruction. Chromatic Aberration is light out of focus light.
4. Aperture is not as simple as you say. In terms of light gathering it goes by area and reflectivity. A 25% CO only reduces the area by 6%. In terms of resolution, aperture is aperture, the Dawes limit for a 6 inch scope is not affected by a central obstruction.
In general, I believe refractors make the best small scopes, assuming your willing to pay for ED optics. They're efficient and they a versatile. But they do not scale up well.
I really don't know the demographics of telescope ownership and use. Certainly there are many who use SCTs and Maks for their compact performance, many who use Dobs and other Newtonians for their simplicty and optical prowess. And there are many who refractors.
I think most amateurs own scopes of more than one type. No one type can do it all.