> The most important distinction between mask models is that some models have valves / vents and some do not.

The most important distinctions also include:

1) Fit. This matters a lot.

2) Nano versus electrostatic technology.

3) Filtration level. "N95" advertised isn't always 95% in reality, and some are 99+%.

4) Impedance to airflow

#4 is more than just comfort it determines how much air goes around the mask.