Include Adaptever, GLV and Super T1 to your list.
At any specific voltage, any of the
devices you mentioned, or that I added above, will perform about the same. All things being the same (i.e. atomizer type, battery,
e-liquid), a AdapteveR and Screwdriver, for example, would create a similar amount of vapor and throat hit. What your decision really boils down to is style, design, button placement, adapters for different atomizers and overall value. Whereas you can pickup a Super T1 complete with
batteries, charger and atomizer for around $145, a GG Transformer will cost near $200 with nothing but the metal tube.