Personally I prefer corns, which is why I have two of them now.
Kings are pretty active, but that extends to when you hold them. I've never yet encountered a kingsnake that was calm when out of its cage. From what I know, ratsnakes are even more active, and I have no personal experience with milks.

Corns would be the best way to go if you want a good snake for viewing and handling. Also they tend to be regular eating machines once established and come in the widest variety of colors so you'll have a great choice.