I too have been boinked on the back by a short backstop, and it didn't injure but it hurt for a bit. For years I had both a TM and an All-Star MVP4000, for those situations (and on hot windy days when it was actually better ventilated). Would probably wear it 20% of the time, less so last few years as the # of games on those older fields has lessened. Now, I have an F3 TM and love it, selling the HSM last year for a deal too good to pass up, but wouldn't wear any TM other than the F3 in place of the All-Star.
With all due respect, I have heard on occasion of this research but have never once seen a citation or summary of an actual study. I'm not saying it doesn't exist, but I simply do not believe it's anywhere near definitive. There's also research on the other side - Brad from All-Star himself posted on these very pages years ago about some of their research. There are some angles and scenarios where a traditional mask is as good or slightly better, according to them, many where the more angular HSM is better. Yes, they were a manufacturer and worthy of a grain of salt, but he at least put his name and rep on it. And the All-Star and F3 HSM are the only ones I'd ever use - very low opinion of the Shock F/X due to durability concerns, the multiple stories of woeful warranty service, not to mention that big ole flat forehead area on it.
Frankly, I think the idea of a TM spinning being protective is - well, far more old wives tale than physics. If it spins the wider, flatter TM, it may be a tangential shot that would have either missed a high quality (All Star or F3) HSM altogether or harmlessly glanced off. If it's more frontal, even if there's some spin, the direct force is already transferred to you in either case. I just don' t buy it as a material advantage. I would love for more research - on either side - to be more publicly avail, but I doubt the differences for either (caveat: a high quality example of either, not some cheapie plastic bargain rack helmet or budget TM with light foam) to overcome what someone feels comfortable using.