Micro groove is OK as long as you have fit. I sold the stupid Marlin .44 mag because of the twist. Had Ballard rifling but measurements showed less lands and grooves but the same dimensions, .003" deep grooves and bore the same as micro groove. More lands and grooves of the micro groove is better. If Marlin would reduce the bore size so rifling is .006" in the Ballard, cast would be better.
A good round ball ML needs .010" deep grooves.
Many good revolvers only have .004" deep grooves and would benefit with deeper for cast. I would love to see .006" in a revolver.
I would rather have a micro groove in a Marlin. It affords more grip.