Well, I’d refer to @RAyers, who explains why speed and fence height do not significantly change the mechanics of equestrian falls.
I also think it is a huge misconception to assume that the falls sustained by amateur riders are somehow “little” falls compared to the falls sustained by upper level riders. That’s denial–regular amateurs can and do have horrible falls that can result in serious injuries, hospitalization, and death.
Also, if you have two types of vest to choose from and one type has good data and the other does not, why would you choose the one that doesn’t have good data? I’m genuinely curious.
Air vests are problematic for several reasons.
Air vests do not protect against accidents that occur on the ground while handling horses, right before getting on or off. Most of us middle-aged ladies handle nice horses, but a hard shell vest can offer protection should something unexpected occur.
Air vests do not provide any protection for accidents that happen while mounting and dismounting. This is a very common type of accident for adult amateurs.
Air vests do not offer any protection should you forget to clip in or should the vest malfunction and fail to deploy.
The sound of the canister releasing can spook a horse and worsen an accident. I’ve seen horses kick out towards fallen riders or bolt. Should a rider become caught or tangled by a piece of clothing or tack, the noise could be very deleterious.
The sound of the canister releasing can spook other people’s horses and cause other people to sustain accidents.
Should a horse slip, trip or otherwise fall in tandem with the rider, or rear over sideways or backwards, or have a rotational fall over any size jump, if the rider does not separate enough from the horse the vest will not deploy and will not offer any protection.
We do not know how air vests change the trajectory of falls or how they alter the forces on a persons C-spine on impact from a fall.
Here is the article I’m referencing:
https://pubmed.ncbi.nlm.nih.gov/31160233/