Best MM?

You cannot go wrong with the Zephyr. I have a few Sound-Smith products (not the Zephyr) and IMO they have the most natural sound and are a terrific value. I have an Ortophon 2M Black and I don’t use it (probably will sell it), it sounds too "hard". I had the Shure and replaced that long ago. I also have a classic Signet TK-7SU and an MA 2002e by Micro-Acoustics that are in their boxes.

I use the Sound-Smiths all the time. They sound the best to me. I’m sure all the carts mentioned are good, but like I said, you can’t go wrong with the Zephyr.
Rollin

@dhcod What cart are you currently using?

I've been an IQ3 user for several years - really fabulous MM cartridge. Tracks impeccably, full range balanced frequency range, dynamic & lively but also smooth and non-fatiguing. Deep soundstage with pin-sharp imaging. I got this as a 'damaged stylus' IQ2 for $60 & added the IQ3 stylus (& easily repaired the 2).

Goldring 1000 series styli also fit IQs & I use the 1042 a lot - the Gyger2 sounds pretty similar to the full IQ3.

Also use a Roksan Corus Black, again sometimes with a 1042 stylus. Definite family resemblance to the IQs & another excellent MM. 

I find the Ortofon 2M Black to be much more demanding of hyper-accurate alignment to get the best out of it. It's superb on my SL1200G, fast, dynamic and silky smooth but edgy  on all the other TTs I have tried for some reason (Linn, Clearaudio, Rega). I am very careful with setup, alignment & especially azimuth.

Finally, another excellent MM is the AT150ANV which I purchased new when launched but either rare or pricey now. Similar to the 2M Black but slightly 'leaner' sounding. 

Maestro 2 is really good, I traded up to the Charisma V2, even better, outstanding actually. Very happy with it, will definitely keep it for as long as it lasts.