As a long time breeder of angels, I have some pretty strong personal opinions on the topic
Over the years, my likes & dislikes have changed, but a few things have remained the same. Popular color varieties come & go, but the things that separate "quality" angelfish from what you find in a typical LFS remain the same. Personally, I look for long, straight fins, equal length in the dorsal/anal fins and the ventral fins, straight body lines along the head & belly, clear eyes in proportion to body size, and finally compliance with the phenotype under which they are being sold.
I have raised numerous color/fin varieties of angelfish, but I must say that my personal favorite is the standard silver variety with normal finnage, 4 black bars, and bright red eyes. My second favorite would be a true double dark angelfish (sometimes sold as "velvet"). My least favorite would be any variety sporting "super veil" fins or pearlscale. But again, that is just my personal feelings & I am fully aware that peoples taste in angels vary.