One stereo or two (stereo and mono) cartridges?

I beg to differ with "spatialking", where he states "Also note that many mono recordings are not RIAA compensated, so spending a lot of money for a mono cartridge could be somewhat of a waste." The statement has merit if you are talking about 78 rpm records from the 40s and earlier. However, once we entered the LP era in the early 50s, all LPs are frequency compensated according to one or another algorithm, and by the mid to late 50s, all LPs I know about were RIAA compensated. I guess some British companies continued to use other algorithms longer than we did in the US, before standardizing on RIAA. Moreover, frequency compensation does not take place at the level of the cartridge; this is done in and by the phono stage, so in a way the point is irrelevant. My opinion is that there is much to be gained, not just a reduction in noise, by playing mono LPs in mono and that on the other hand there is no real need to invest in a mono cartridge IF your line stage has a mono switch. Just flip the switch for mono LPs, and you will hear mono LPs with much improved fidelity, compared to playing them in stereo with a stereo cartridge. That’s just my opinion. Yes, you might squeeze out another dollop of wonderfulness if you use a mono cartridge; I am not going to dispute that, but also consider that you are then comparing two different cartridges, as well as two different processes.  Anything goes in that regard.

I can unequivocally state that my mono LP’s sound better (sometimes much better) when I install and play with my mono cart vs my stereo carts. 
 

@lewm thank you, this is exactly the type of information I was looking for. I do have a mono option on my Rega Aura. I tried it at the beginning and did not notice much of a difference, so stopped using it. I will give it a fair trial.