The latter is the canonical way to refer to the field, and its unclear when, if ever, [deep-network] would be preferable. Its a small change, but it'd help avoid very odd sounding questions like "What is Deep Network?"
deep-learning is preferred, then
deep-network should be set up as a tag synonym for it, that way if anyone tries to use it, it gets mapped to the preferred name. We need someone with 1250 reputation to do that.