I do not even use a mono switch. I play mono records on the same table I play everything else. I do use a separate cartridge for 78s which is mandatory because the groove is much larger. Modern styluses on high end stereo cartridges cause less record wear due to their larger contact area. The best way to listen to mono records is off axis, out of the listening position. A system capable of the best imaging is weird to hear in mono mode from the listening position. It is like listening through a crack in the door, a narrow vertical line directly in the middle. Off axis the sound opens up, unpacks itself. There can even be a quasi image.
Turntable choice for mono records
I am planning to purchase a second turntable dedicated to playing my 500+ mono records (mostly post-1960 pressings or reissues) and some of the lesser quality stereo records to limit wear on my reference system (Basis turntable with Benz Micro SLR Gullwing). To support cartridge switching, I am exploring tables with a replaceable arm or headshell. The mono carts I am considering, e.g., AT33, Ortofon 2M, and Shelter 501 II, are all considerably lower cost than my current cart. Given the price differential on carts, would I notice a sound difference between a Technics SL-1500C, SL-1210GR2, and the SL-1210G? Or between the Technics line and the Luxman PD-171A or other manufacturers?
I am especially interested in the opinions of those who find a notable sound difference between stereo and mono carts. What turntable and cartridge (below $2k) provides the greatest differential?