Same here - It's a fun ride, though, and I plan to keep doing it long after they're all on their own.
Great, now I have to pull out my old, mostly-unused engineering degree..
This part makes perfect sense, and I doubt anybody can argue with this (well, maybe to the degree "many" vs "some")
The goal of any mask is to dissipate energy to reduce the impact to your face. There are different ways this can happen, in order from the best to the worst.
1) Don't get hit. This sounds silly, but the truly best mask would be so close to your face it wouldn't get hit unless the ball was going to hit you. The bigger the mask, the more it gets hit. TM's are better than HSM's on this principle, with the low-profile ones being best.
2) Ball gets deflected, going at a slightly different angle than it started with - the smaller the angle of deflection, the less is absorbed by the mask, and subsequently, by your face. When it works, this method is best, because the ball dissipates its own kinetic energy. The best design for this would be a long, narrow angle wedge, except that would violate #1. Straight-on shorts really can't do this well, and we have to plan for that. HSM's tend to have less straight-on spots than TM's, so they would be better for this.
3) The energy gets transferred to the mask as the mask is knocked off. If your mask goes straight off the back of your head, the energy was not transferred to your face, and that's what we want. *Some* of that energy can go into spinning, but merely spinning a mask doesn't keep that energy from going back to your face. We can look at it in terms of XYZ coordinates, but faces aren't perfectly flat, and neither are masks, so that makes the math quite complicated, but any energy that is transferred toward "something besides your face" is a good thing. TM's can do this, HSM's can't.
4) The one we all dread - the one that's straight to the face, and the energy *will* go to your face in some way or another. Then it becomes a matter of pads (and in the case of F3, springs along with the pads), which will dissipate the energy over a greater surface area and a greater amount of time. In exactly the opposite as #1, we want more space and more padding when this happens. Create a mask that will instantly materialize 6" of a sofa cushion in front of your face, and you're perfect for this one. I've never used a HSM, but my understanding is that most of them are fairly bad in this area. TM's vary a LOT, and can even change with time as pads get worn out, and perform differently in heat or cold or wet.
5) The X-factor - balls coming from other fields, bouncing off backstops, bats breaking, or anything else coming from not-in-front-of-you. They're rare, but do happen on occasion. HSM's with the obvious advantage on these.