And, to be clear, most distributions no longer use Sendmail as the default. Postfix is the default on RHEL/CentOS/Scientific Linux. exim was the default in Debian for many many years, not sure if it still is. Postfix is the default on Ubuntu, I believe. I can't think of any distros for which sendmail is the default MTA.
Once qmail has been patched up to modern MTA standards, it no longer has the pedigree of being built and maintained by djb. I don't know the people who maintain the huge patch sets for qmail...maybe they're good. I know Wietse is more than competent.
But, that may be what you're getting at with "Postfix is the saner default choice for normal users". We support all of them (Sendmail, Postfix, qmail, and exim) in Virtualmin to varying degrees, but we configure Postfix, by default, and very strongly encourage its use over the alternatives (mostly because we know Postfix so much better, and because so many more people use it). About 95% of our users stick with Postfix, though we do have some users of all of the others.