thanks for stating the important distinction between literary and textual criticism, W, it is frustrating to see the two being unconsciously blended so often.
as for the Cambridge G&Ys, the commentator is allowed to do what he/she wishes. never is it the case, however, that important textual alterations are left unnoted. having had a quick look:
Garvie’s Odyssey VI-VIII, Sommerstein’s Eumenides, Hunter’s argonautica III, Kells’ Electra, Shackleton-Bailey’s Cicero’s letters, Martin’s adelphoe, MacCary and Willcock’s Casina, Grandsen’s Aeneid VIII and XI, Hardie’s Aeneid IX and Kenney’s heroides XVI-XXI have full ACs (i refrain from ‘apparatus critici’). Martin and Woodman’s annals IV has a very minor one.
The following have condensed notes on where the text differs:
Carey’s Lysias (p.13 noting discrepancies from Hude’s OCT)
Murray’s Ion (p.32 noting discrepancies from Burnet’s OCT)
Rusten’s Thucy-d II (appendix of discrepancies from OCT pp.247-8)
Morton Braund’s Juvenal I (pp.40-2 noting differences from Clausen’s OCT)
Carey and Reid’s Demosthenes (p.20 refers reafer to OCT and Budé)
Fantham’s Fsti IV (noting differences from Teubner on p.52)
Thomas’ Georgics (2 vol) (differences noted pp.33-4 in vol.1).
the texts are intended to be more analytical commentaries than reworked texts, although some of the finest textual critics of the modern age - Kenney and Shackleton-Bailey, to name but two - make the most of their abilities to great effect.
regarding the editions, I think in textual terms one would have to rank from top to bottom: OCT, Teubner (although for a good number of authors better than the OCT version, if one exists), Bude, G&Y, Loeb (although Goold’s Manilius and Shack’s Martial and Statius are superb). this neglects many of the fine Oxford commentaries which have appeared in a sort of series (cf. the several Euripidean efforts).
as regards lunate sigma and iota adscript, i think the arguments are most concisely voiced by West (against both) pp.vi-vii of his Theogony and Barrett (for both) pp.vii-viii of his Hippolytus. i have to follow the better scholar.
i thought that Prof Diggle would have a stronger opinion for his constant use of the latter in his 3vol Euripides OCT, but it comes largely down to aesthetics for him, and matters of font trouble him little!
i have Porson’s editions of his four Euripides plays, and the font is clear and attractive. he does not use a lunate sigma. a much more difficult Greek font to read is that which Bentley uses in his 1699 Dissertation upon the Epistles of Phalaris (which i acquired the other day). it takes some real work to decipher it, but then again a man with the mind of Bentley can type Greek how he pleases!
~D