Ok here's what I think so far of GT4 v Dvarw DL. Remembering I've only had the GT4 for days and been vaping Dvarw DLs daily for over a year.
One of the things I love about the Dvarw is how bullet proof and simple it is. No moving parts - no juice flow controls, AFC rings etc. It's just a dead simple atty with great flavour and smooth air. Once you know how to build it to suit your vape you get it right every time. Never leaks, floods, dry hits.
The GT4 is a completely different story. It's complicated in a way and has two completely different AF channels hitting the coil. You can choose one, the other or a combination. It also has juice flow which works really well but is an added complication with more moving parts /O rings etc to fail.
The flavour is great on both but it takes dedication and a bit of persistence to get it right on the GT4. I'm not there yet but getting close.
If I had to choose one I'd go the Dvarw but the GT4 is a classic and also a great single coil RTA.