I'd have to favour a DJ all the way. They aren't all desperately uncool with cringeworthy taste and a love of the sound of their own voice! My DJ was perfect - if you are worried about how they might "behave", you aren't picking the right DJ for your party. A DJ is something to be researched, to find one who fits your vibe and shares your taste, who can read a crowd and direct the evening. Trusting my family and friends to make appropriate music choices was never going to happen. With a juke box, people can choose what THEY want to hear, with no reference to what's currently on, what's already been played, and so on. A DJ adds something a juke box can't, intelligence :)
Don't be fooled by their innocent looks. All Emmas Are Evil. And they're coming for you.