I shoot .38s in my .357 mag bedroom gun and then load 357s back in when it goes back to the bedroom for home defense. It's all about being comfortable with the gun when you turn to it for defense. The only time the extra power/noise of the .357 won't be detrimental to comfort is when the adrenalin is high from the fight response. Then the extra stopping power and noise will serve their purpose.
Oddly enough, I just picked up some .357 CCI Blazers at a local shop for $4 less a box than the same brand and weight of .38 +p ($21 vs. $25 a box). I don't know if that's just a result of the current price fluctuations or what.
Yep. In times of scarcity, the round that fits more guns will get the bigger jump in price and this kind of inversion can occur. The extra powder cost and lower market share of the .357 become insignificant when demand outstrips supply for the cheaper-to-make .38.