There is so much more choice in ammo with .357, besides, how can you give up compatibility with the .38 spl for target practice with the same gun?
Part of the desirablity of the .357 is that it is considered pretty much the most desirable self defense round, (with all due respect to the .45)
I believe it is because of ammo development more than weapons development.
For comparison, the .44 magnum is actually less desirable for self defense, obviously not because it offers less power, but because most rounds were developed for hunting and defense against large animals. I believe .41 ammo is developed with the same purposes in mind.
For self defense, most .44 rounds tend to overpenetrate due to the fact that they were designed to kill large animals.
I could imagine the .41 offfering a verynarrow choice of off the shelf ammo.
(Remember to always use off the shelf ammo in self defense)