Well there are a few...
1) improvements, Merc came up with the warm manifolds system which reduces condensation in the exhaust system but adds hoses
2) convenience, single point drain adds a lot of extra hoses and fittings, but to me is not an improvement, because they can clog due to rust flakes
a true improvement would be standard closed cooling, that would eliminate the draw back of the single point drain and extend engine life.
