The CT-93 is a revised and upgraded CT-91.
If the Reference Master Mechanism and motors are the same (but probably somewhat revised from the CT-A9 1980s biggie), the main differences lie in the electronics and added functions : Super Auto BLE and... Dolby S !
Dolby S is the ultimate consumer version of the successful Dolby B NR system : when first launched in the early 1990s, it was only implemented in high-end recorders, as requested by the Dolby labs. It was later on used elsewhere in the lineups but probably came too late to really replace the good ol' Dolby B.
Not to mention dbx.
Or CD-R !
Also different is the erase head which went from basic ferrite to double-gap ferrite plus Sendust guard.
Resulting specs are slightly upped by the Auto BLE system but the rest is the same : cast-iron transformer, honeycomb copper-plated chassis, honeycomb feet, single-crystal oxygen-free copper wiring, select componentry and three-piece honeycomb cassette stabilizer (as in Sony's contemporary TC-K990ES).
The original T-858 japanese model - non Elite, of course.