I want my AAS to supply more air than I can possibly use because I'm only going to use it in some kind of an emergency situation. An Air 2 is a compromise solution. Compare the published air delivery figures and you can see that the most basic SP second stage will deliver half as much again as the Air 2. R295 1400 lpm, Air 2 906 lpm.
Just how much air can one possibly breathe even in an emergency situation? Anyway, what is your opinion of the R190 as a backup second stage?