A good way to think of the difference between the two is that the esoteric paths are paths of effort. The mystical paths emphasise letting go of effort. In most cases even the simple effort of single pointed meditation needs to be released to allow true contemplation.
As an aside, I first encountered this process described in these terms meditation and contemplation, from Namkhai Norbu explaining the difference between threkChod and shine in Dzogchen. I later encountered the same exact description when reading Theresa of Avila. I found on Sunday when hanging out with JR that Norbu borrowed the terms from Theresa.