I think the difference in injury accident likelihoods between motorcycles and Spyders is not really relevant. In both cases you don't have a protective crumple zone cage around you, with seatbelts and airbag systems. I suspect that severe accident consequences are closer together in likelihood Spyders and motorcycles in number with both being far, far higher than severe accident consequences in a car. If I'm in a likely moderate collision in a car compared with a motorcycle and a Spyder, I'm walking away from the car and the difference between the motorcycle and a Spyder might just come down to slight differences in severity of pretty much the same types of injuries. Where the Spyder wins over the motorcycle is in minor tip offs at slower speeds.
So, when out on the road, motorcycle and Spyder, I wear a jacket and gloves rated with current EU protection standard armor.
Having walked away from absolutely horrendous motorcycle accidents in the past, I can personally attest to the protection afforded by properly certified riding gear with inbuilt armor. Now, on my Spyder, I do use a vented Klim jacket with inbuilt armor in summer with Alpine Stars summer gloves, stout jeans, steel toe capped over the ankle boots, and a modular Shoei helmet. My wife wears the same. This is less than the full leathers I wore on my motorcycles because the speeds I ride at are much slower and I feel the heat more, so overheating is now a major concern at my age. This is a risk v. reward calculation though. When the weather cools I'm back to a high quality leather jacket with built in armor and stouter gloves.
I'm not saying everybody doesn't evaluate risk in their own way and come to their own conclusion, that's a personal thing. This is just how I feel about the likelihood of being in an injury accident with a Spyder versus a motorcycle, and compared with a car, and how I dress to mitigate the risk for me personally.