As I mentioned, I know nothing about the chemisty of the coolants, but when I asked one MB mechanic why the MB stuff was preferable, his answer was that MB expects the life of their engines to be in multiples of 100K--400K in the case of most of the diesels. The expected life of a Detroit engine, especially the gassers, is somewhere between 100K and 150K, and the ricers somewhere between 100K and 200K.
His point was that, for short-lived engines, there's little reason to be concerned about how the antifreeze is affecting the cooling system. If you want your engine to live to an old age, use the MB stuff. Again, I don't know the chemistry well enough to say what it is that makes the MB stuff better--I presume it's the anti-corrosion materials.
I also understand that MB and Dexcool aren't quite so bad on the environment when you finally dispose of them, though again I couldn't explain why.