Actually, to compare Lyra mono, zero mono, and EMT mono, you need to have original mono recordings, which were made in the era of mono (not monos made in the era of stereo). In the 50s, especially early 50s.
Since you have the EMT, you can play them through mono switch, or if you have a Miyajima step up, then use step up to play through stereo switch. Do various mono cart compares with combinations of the mono switch on and off. And compare with a stereo cart playing mono.
I haven't done these, but with an EMT phono, you can. The technical reason given on forums is that Miyajima mono has no vertical compliance and tracks horizontally while dual coil monos like Lyra which sum up have vertical compliance too. Whether the technical reason is right or not can be verified only in listening.
Michael Fremer, Art Dudley, Jacob helibrunn seem to be recommending the Miyajima mono. There is also the EMT- the older OFD 25, the newer TMD 25, and there is the Clement from France. All of these are quite low priced. One day I would like to try out all.