I don't actually think there should be any debate, as M. egregia, as it is now applied, is just one form of M. lasiacantha.
The name of M. egregia was not validly published, as no locality was ever given and a type was not designated. The Backeberg description calls for 6 central spines and 50 or more radial spines, in several series, white, topped sometimes rose at first.
It is always difficult to count the spines on the Lasiacanthae species, but I don't think your plant comes anywhere close to those sort of numbers.
Unless you know where the seed originally came from and that there has been no accidental hybridisation, it is just safer to stick with M. lasiacantha.