I've been reading articles on Tironian notation and what is known about Greek tachygraphy. The most careful discussion of the topic I've come across yet is the article by F. W. G. Float, "On Old Greek Tachygraphy", in the 1901 Journal of Hellenic Studies.
Float points out that different shorthand systems are designed to accomplish different goals: Tachygraphic systems are designed for quick writing; Stenographic systems are meant to preserve space. Either type of system may emphasize clarity or secrecy to some degree.
Tironian notation is simply amazing. Tironian notae encode a modicum of phonetic information--as much as is needed to distinguish a less common word from a more common one--but I would guess that the average nota encodes less phonetic information than the average Chinese character, arguably making the notae tironianae more ideographic than Chinese.
Many of the classical tachygraphic systems seem to encode syllables. In my last post I had said that there were too many symbols in the Rohonc script for it to be a syllabary, but I was thinking of syllabaries that are based on (C)V syllables. For comparison with Latin, where syllables are more complex, I took the book of Genesis from the Vulgata, divided all of the words syllabically, and counted the unique syllables. There were 1139--roughly the same as the number of unique Rohonc symbols. It is not impossible that the Rohonc script could be (partly) syllabic.