HBO will give you more original series, many of them excellent. Like Game of Thrones which is playing now. Also good boxing matches, and of course, the movies.
Max has an original series, Strikeback, that I liked, but overall I only subscribe when that series is playing.
HBOGo is slick as hell. Not only does it work well, but you can also view some of their older series that are not available anywhere but on DVD/BluRay. Like Carnivale, Deadwood and others of the older series, and also all the episodes of the current series. Like Trueblood from the beginning.
Max also has the same thing, but I didn't find myself using it much as it didn't have much I wanted to watch on it.