Fit is critically important. There is no point in having an advanced filter material if the mask fit itself is leaking air everywhere. >"An N95 is more protective because it has a better face seal in general than a KN95 or a KF94," N95 does not require manufacturers to test for fit. However, the headband normally ensures a better face seal. KF94 has a fit-test requirement, but it's bar is low -- 11% leakage to pass t…
>and is easy to breathe in with My understanding is that for Covid your mask is expected to filter exhalation, protecting others from any virus you may have in your system. My understanding is that masks do very little to protect you from inhaling unwanted virus carrying particles. Of course, it seems to me that a good mask should really be doing both jobs at once, with a good seal. Which means no beards and headband…
Once you're dealing with exposure to an environment filled with the fine airborne particles you need a well-fitted N95 or better to protect yourself. Although the virus itself is tiny it's traveling in particles closer to 1 micron which N95 type filters work great for. You can still be infected through your eyes but as far as I know that's very rare in normal non-hospital settings.
So that's self-protection, but why bother? It's true that at this point most people will be exposed eventually and with three shots of the mRNA vaccines people are unlikely to end up in the hospital. Several reasons. First, slowing rate of transmission will reduce overloading the hospital system. That saves a lot of collateral damage to people with otherwise treatable problems when they get turned away due to the crowds. Second, if you are unlucky enough to get sick enough to need a hospital bed you want that to happen when there is plenty of capacity, availability of drugs, etc. Third, the treatment regimens keep improving as the medical world learns better treatments and better drugs become available. Fourth, how sick you get appears to vary with how much virus you are exposed to. So even if your PPE is not perfect you can reduce your odds of serious effects when infected. Around half of people infected experience long-term lingering symptoms and there's evidence even in kids that number is not negligible.
It's pretty clear masks are effective both at an individual protection level and as a public health measure, I'm not sure how they got turned into such a political hot topic.