I don't work in the biological sciences, but my money's on the variolation argument more than the humidity behind your mask. https://www.nejm.org/doi/full/10.1056/NEJMp2026913

Here's why:

Humidity affects the dessication of droplets, which in turn shifts what fraction become airborne (as aerosols) or settle out (as droplets). In the tiny enclosed volume between your face and your mask, that difference doesn't matter, because the whole volume is exchanged multiple times with each breath.

Masks reduce the number of viruses that you're exposed to, so even if you are exposed to enough to make you sick, you get less sick than you would have otherwise.