That depends...which Newtonians...which APOs...and for what?
- the refractor is closed -> less tube current
- the refractir does not have any obstruction -> higher contrast, better FTM in medium frequencies
- the refractor has some chromatism/spherochromatism, the newton does not
- the refractor has a much larger illuminated field compared to common newtonian. The Newtonian requires a very large secondary to compete, which significantly impacts the contrast in visual use. At higher obstruction than 20%, the difference becomes obvious in visual use.
There are so many use cases...in some the refractor is prefered in some others the Newtonian better performs...
Its like comparing two different wrenches of the same size.
A flat open end wrench and a L shaped socket wrench for instance.
Both can do the job most of the time, but sometime one is prefered or even is the only way to do the job.
From what I can gather from your views, you didn't read my article, listed below in red, followed by the flowered smiley, signifying peace.
I addressed central obstruction issues and demonstrated that, according to Richard Suiter. that anything below 18% central obstruction is imperceptible to the human eye. While there may be 10% of folks out there who might see that difference, the advertisers like to leave the impression that you are in that 10% and should buy an apo telescope. And if you wish to argue the point with Richard Suiter who set that 18% criterion, you go right ahead; I have his email if you want it as long as you promise to post his reply. I can't wait! If you don't really believe him, I can quote from another source that some very well-known and erudite optical people who set that figure as high as 30%, while only one sets the numbers as low as 10%, so go figure.
You are to be commended for acknowledging the apo problem of spherochromatic errors. These are more important that others, less fair than you, wish to admit.
As for wider fields, you have me, but with this provison; most if not all apos are almost, but not quite, apochromatic at the center of their fields; that spherochromatic stuff messes images up away from that center. Indeed, the scientist Abbe came up with the first criterion for a lens to be an apo; that is first: it will bring three widely spaced colors to a color free central image free of spherical aberration and second, it will be corrected for coma in only one color. So, once again, go figure. As Abbe was the first to work this optical problem out, perhaps apos should be called "Abbe" telescopes, and you can use a capital letter. So there you go
Please note that my article demonstrated that in the formation of the Abbe Disk, there was no perceptable difference between a Newtonian reflector and an apo of equal aperture. That's right, equal.
Speaking of spider diffraction, there is none in the reflector that I described and built, not because I took the easy and fallacious way out with a spider that spread around that diffraction; instead, I made an optical window to seal my tube and hold my diagonal. There were other things that I did, even considering the quality of polish in my telescope's optics. Indeed, I even considered other deficiencies in both the apo and the Newtonian and fixed them in my Definitive Newtonian, issues that can never be addressed by an apo maker who knows the value of time and cannot waste any. I can understand that. To make a fair profit, he has to be this way. Otherwise, his employees don't eat, pure and simple.
So there you have it. Please read what I wrote and remember, I really did the research and even more since! I can forgive you as you jumped into a discussion on page 16 derived from the substance of my article, "The Definitive Newtonian Reflector" and didn't realize what you jumped into.
In passing, please do not capitalize apo; there was no person named "apo" who invented the design, and using capitals implies an importance not earned; an apo is just another optical design.