Actually it would surprise me if the recent vintage, Chinese made SCTs are better than the vintage ones considering that the vintage ones were made here, in smaller volumes, and were much, much more expensive than similar sized one available today, meaning that there was margin to be had and an incentive, therefore, to invest more labor.
Also, the science about large CO's not being optimal isn't theoretical or opinion. It is fact. There is no question, for example, that the star images produced by a 6" MCT with a 31% CO differ noticeably (for the worse) from the star images seen through a 6" MN with only a 17% CO. If you care about the science as to why this is factually the case, here's a good basic discussion of the effects of CO and on airy disk size and the amount of energy scattered from the airy disk to the diffraction rings. This scattering represents light that isn't going to where it optimally is supposed to go - your eye as a focused image.
I've owned and used many examples of each design (Newtonian, SCT, MCT and refractor) at all quality levels (cheap, commercial, premium), and in my experience the science and the experience coincide. I cannot tell you how many dozens of times a member of the public (non-astronomer) will comment that the view though a 10" or 12" commecial Dob or 4" commercial-grade APO is "sharper", "clearer" or "better" than the planetary view through an adjacent 12", 8" or 6" SCT. Hardly "5%" or "Nth degree" differences when a complete neophyte with no pre-conceived notions, and no experience, easily sees the difference predicted by the science.
I love SCTs for their virtues - the unique combination of affordability, portability,mountability and availability. I don't count optical superiority by design as one of the virtues.