mono cartridge vs stereo

Lots of the music I want to listen to is in mono. At present I use my stereo cartridge with the mono button pressed on the phono pre. I can't find much on the differences in this vs dedicated mono cartridge. Any insights/experience would be appreciated.
I ended up buying a ortofon mono 2m and hear a big differnce! Thanks for the advice, I now look for momo vinyl in the shops! Just picked up Miles Davis 'round midnite!
Gondo, A mono phono stage adds yet another layer of complication, in terms of decision making. First, why use a mono phono stage if your "mono" cartridge is naught but a stereo cartridge that is internally strapped to produce a mono signal? In that case, one's "stereo" phono stage is merely processing the very same signal to produce two mono output signals, to drive two speakers in mono. I actually like that, because it produces a bigger more room-filling sound than I can achieve driving only one speaker of a stereo pair. Now, what might be the advantage of a mono phono stage? I guess it would be that the two stereo channels in your stereo phono stage are not exactly matched, thus producing subtly variant signals that end up as two slightly different signals on your two speakers, maybe robbing some ultimate fidelity. But if you worry about that, then why couldn't one simply abrogate the output of one channel of a stereo phono stage and thereby use only one half of it, to drive one speaker?
Do OMA suggest driving two speakers with the mono output of their mono phono stage, or just one? Probably the latter.

One could write several more paragraphs on the other things to consider, like for true vintage mono LPs not equalized for RIAA standards. In that case, if the OMA product has selectable equalization curves, therein would lie an added value. But it's a sticky wicket.
Thanks Lewm, finally someone has shed some lights :)
Just realized, unless I missread, when somebody shared their experience with mono phono preamp (Art Dudley in Stereophile and Jacob H in absolute sound online), they didn't mention whether they listened to 2 speakers or just one.
Do you have any experience listening to mono phono preamp via 2 speakers vs 1 speaker?
Grado makes a couple of mono cartridges in their Prestige line: the MC+ w/conical stylus for $90 and the ME+ w/elliptical stylus for $150 .
I think results are pressing dependent. I've been checking out a DL102, a true mono cart similar to a 103, only a HOMC. This has a .7 spherical and vintage pressings sound much better with it. The entire presentation is more coherent, natural and quieter.
On modern mono pressings, not so much. I'm used to a more analytical sound and with modern pressings the 102 can actually sound worse.

Ortofon has two - 2M Mono carts. Unless the description is poorly translated the output is strapped. They are also described as true mono, so it's unclear exactly what they are. The regular one has a .7 spherical and the SE has a shibata. This was obviously designed for modern mono pressings made with a stereo cutter like the Beatles box.
They also have a Cadenza Mono which has a fine line, but some of the SPU have various sized spherical.