I find they're not great for beginner groups. I go with a sort of "sandbox-lite" style in those campaigns. There is still room for meaningful choices, but the options are somewhat limited and obvious. Otherwise you tend to get a kind of paralysis by analysis, because they don't yet know the style of cooperative storytelling that drives a true sandbox game.
My home campaigns, on the other hand, always start with a fairly structured mini-arc, to get things rolling, and then just evolve according to player interests and choices. I find them more fun to run, because I get to discover the story along with the players. But I have to really be on my toes, and willing to put in the work on short notice when the players suddenly decide, as they did last session, that they need to head straight to a city that I don't have prepared, to follow up on a family complication that I only just learned about.