Was I wrong in my analysis?
I'm a former English teacher, have some training in scientific method, and am sometimes also a literalist, so when you ask a question like "Was I wrong in my analysis?" I want to examine that.
If your conclusion had been that Diamond's DA40 is safer than either the SR20 or SR22, then you'd be in safe territory. The Diamond fleet has a stellar safety record, there's no doubt about that. Cirrus went through a time when they had an accident rate that was below average, though they turned that around and now the accident rate is about half of the GA average. Clearly, the DA40 is a safer airplane.
I think that if you had examined why the DA40 is safer, you would have found the information that would show how you're not making the appropriate comparison. It weighs about 15% less than the SR20, stalls 10% slower, and cruises 10 knots slower. It will simply have less energy in a crash, and less energy means less damage and chance of injury or death. The comparison to the SR22 shows an even bigger difference (35 knots slower, weighing 1/3 less). The main commonality is that they're both modern designs, but this doesn't make the DA40 a good control to compare safety of the bigger, faster SR20 or SR22. They're performing different missions.
There aren't a lot of facts or data in your presentation, so that makes it tough to follow along to the leap you make in your conclusion. The little bit of safety data is cherry-picked from Diamond's marketing materials, and using a metric that is not the industry standard (I'm not even sure what "1000 airplane-years" really means). You rightly point out that there are limitations with a BRS or CAPS system, though the deployment envelope was honestly bigger than I would have imagined.
Cirrus did have a fatal accident rate that was much worse than the GA average until about 2012, so it's valid to be critical of that. The total accident rate, however, was (and is) very good. Industry analysis seems to conclude that Cirrus pilots were reluctant to pull the chute, and with that slippery, high performance airframe, were getting deeper into trouble and could not recover. Since then, however, Cirrus has focused on safety training, and now the fatal accident rate is half of the GA fleet, and significantly better than other airplanes in its performance category.
