Maha is far and away the superior mango imo.....in numerous ways. Not only is the flavor superior and more complex, but it doesn't have the splitting or post-harvest anthracnose issues NDM has. Maha is also a much more attractive looking fruit. Both are slow growing and productive trees.
I think NDM is a pretty over-rated mango actually. Its a good mango, but I think it mostly appeals to people who enjoy their mangoes decidedly sweet without much other characteristics.....which I suppose is a lot of people, just not me.
I've got 2 Mahas and 2 NDM #4 trees planted....I might plant up to 5 more Maha trees....the only other NDM I'd like to add is an 'original' (not #4) NDM.