[DavGoodlin]

Great thread - I submit that because the gun arrangement, convergence, deflection, shadow mask and screen are round and without pincushion correction in particular, there are few compromises to overcome.

A perfectly set up roundie has fewer possible geometric distortions which result in near-perfect purity and convergence. Few rectangular delta-gun sets produced mid-1960s through the end of the 1970s could converged without some issues at the corners.

When I started high school in 1978, I wanted a round-screen color set as a semi-daily watcher.
What I had was an RCA Nordholm(?) GG643 with a CTC 16XL chassis and a Channel Master rebuilt 21FJP22 that was already going weak on red.
(RCA's tended toward cyan for sure, Compucat)
I brought this TV into high school shop to follow Carl Babcoke's Tab RCA Color Service Manual book to do color set-up with the equipment I did not have at home.
I rejuvenated the CRT to near equal emission and cut-off, then carefully followed the purity and convergence methods in the book, likely copied from RCA factroy info.
After a week or so of repeated set-up adjustments, I brought it home and I swear it looked as good as my parents' 1971 Zenith 23V" console, which was hard to beat.

I saw many a Zenith roundie working beautifully and ocasionally had to fix one but I never HAD one for myself until getting a Zenith 5304 - ch.24MC32 (thanks again, Tim) last year.