How good can a mono cartridge be...?

Can a modest mono cartridge better the performance of a top-of-the-line stereo cartridge?

I am wondering if anyone has practical, first-hand experience with this matter as I am deciding whether or not to invest some money in it. The situation:

1) I am luck to have a top-end tonearm and stereo cartridge
2) I have many mono LPs that sound great on the stereo setup (stereo cart, phono stage, 2 speakers)
3) My turntable will support a 2nd armboard, but my budget would not support a 2nd arm of the quality of my current arm -- nor would I be able to afford a top-of-the-line mono cartridge.

Question: Could a modest arm/mono cartridge actually perform better on mono source material than my top arm/stereo cartridge, all else equal? (No mono switches on the preamp, no mono amp, no single-speaker setup.)

What I'm assuming: If I could mount a top-of-the-line mono cartridge on a 2nd arm of the caliber of my first, then I would assume that it would perform better than my stereo cart on the mono source. Unfortunately, I could not afford to duplicate that setup, so I need to add that "practical" element to the question.

Said another way, on mono LPs...
a) Top arm + top mono cart > Top arm + top stereo cart
b) moderate arm + moderate mono cart > moderate arm + moderate stereo cart
c) moderate arm + moderate mono cart ? ( ?) top arm + top stereo cart

Has anyone experimented with this? Is it worth pursuing for me? I would have to get a 2nd armboard, in addition to the arm + cart.

Thank you!