The Louis Leslie Collection at Rider University includes a Pitmanite response to Gregg shorthand under the title An American Light Liner.
In attempting to assert "the supremacy of Pitman's Shorthand," the author(s?) provide some unintended comic relief in their summary of purpose on page 5:
It is the main object of this critique to show that Gregg Shorthand is a wholly specious system—promising enough, but promising more than it can ever perform—that the facility with which it can be picked up is a fatal facility, equalled only by the facility with which it must inevitably be dropped, given adequate time and trial.
Incidentally, the New York State Shorthand Reporters' Association published a report in 1926 entitled Weaknesses of Pitman Shorthand. (Unfortunately, google books doesn't provide an e-copy.) The Gregg folks must have approved, as they reprinted it themselves (presumably—google books provides no further info.)
But the battle in New York clearly had been raging, as seen in an extended criticism of a paper Mr. SoRelle had turned in entitled "Gregg for Legibility," found in Transactions of the New York State Shorthand Reporters' Association - 45th Annual Meeting Dec. 28, 1920.
I wonder if some of the criticisms here may not have some validity?
I couldn't find any prior reference to the SoRelle paper. I did find one other document by the NYSSRA from 1919 entitled Shorthand Systems Analyzed. (There is another title for the subsequent year, but no e-copy.)
Page 15 provides the crux of the matter with its list of how many schools teach which system. Gregg shorthand goes from zero to 2,163 out of 3,355 by 1918. Dr. Gregg delivers a brief address beginning on this page.
Afterward the book delves into analyses of criteria in assessing shorthand systems, which seem very comprehensive.
Lastly, we have the Chief Scoundrel, that great Rogue among rogues, Mr. Thomas Stratford Malone, again from Mr. Leslie's fine collection. This is entitled Malone and Gregg, and purports to give the "real" story about Script Phonography and all that.
I will not be reading this one, but if anyone else decides to give it a whirl please let us know how it is. :-)