I guess this is for
@bumblebee657 to answer much more than for me, as he has the actual experience.
But to theoretize a bit into the blue:
The cardioid pattern will - with the same on axis SPL - radiate significantly less energy into the room in the mentioned frequency range (250-800Hz)
than a conventional speaker approaching omni pattern. (Omni has 3 times the sound power of cardioid.)
This can be perceived in different ways, depending on room, recording and what one is used to.
- more clarity in LF
- less body and fundament of voices/instruments
- thin and/or bright
- more natural "reverb"/ coloration
- ...
But this is just the general trend, each case might be somewhat different.
There is a thesis about the differences of monopole versus cardioid pattern with genelec speakers from Aalto University by Olli Kantamaa.