2.0mm is 25% thicker and more massive than 1.6mm. Not insignificant.
The heat transfer rate will be determined by the material, which is why we like steel woks (for their relatively slow heat transfer and resulting hot spot in the bottom). The heat capacity will be determined by the mass of the wok. The thicker one will heat up slower but stays hot, while the thinner one would heat up and cool down faster. Which is better in that respect? I don't know. Maybe personal preference and how you will use the wok.