The ML family tend to come from a research background, have a more rigorous approach to typing, solid type inference, and very differently flavored syntax. MLs are functional (first-class functions, expression-orientation), whereas the Algol family in the shape of C, Java etc are mostly imperative. They tend to have nice pattern matching facilities. There's more, but that's a lot of it. A lot of these features have been transplanted into languages that are basically on the Algol tree, so it's often a bit fuzzy these days.