I might be able to pass you a couple of samples of mono records with a stereo cart. I've never minded it but hard panning also doesn't aggravate me past wishing they hadn't.
I own a lot of mono records. I really like how all of them sound and I’ve only ever used a stereo cartridge. In terms of the music a mono cartridge will make no difference. Where the difference can come in is noise. A mono stylus on reads the one side of the groove that the music is on. A stereo reads both sides and can pick up noise on the unused side.
That said I don’t have that problem and good record care should alieviate it. I wouldn’t consider a separate mono cart unless I had removable headshells and a MUCH better system than I do.