Hi Matt.
I think galaxies would be more difficult to compare because the integrated magnitude does not often correspond with the brightness at the centre of the galaxy or at its periphery, due to variations in size and structure.
Having said that, Tony Flanders has an interesting table of peak brightness (PBRT) for the Messier objects that can give you a sense of what magnitude you are seeing at the centre of each galaxy:
https://tony-flanders.com/messier-gu...dex-by-number/