IMO the passthrough (PT) is so much better because of the high voltage. It's a personal preference thing though. I love 5v vaping, which is what the PT is rated at. So it is not necessarily that it works better, it just works better for you.
As for your question about the DAV, imo again, it does perform very nicely! However it isn't because of the VV (Variable Voltage) capabilities. It is because the switch that activates the battery is nice and sensitive so it activates the second you draw on it and it gives a very nice satisfying vape. But, if high voltage is what you like then you should definitely keep that in mind for your future purchases.