Front Sight, Press has an interesting comparison of the .44 Special vs .357 magnum for carry.

It seems to me that .357 is generally cheaper and easier to find.

Back when I was looking to buy a .357 snubbie, I noticed a plethora of .44 Special snubbies at the gun show that day.  I don't remember seeing any such ammo, however.  Maybe it was there and I just missed it, but if it was there, it was hard to find.  No such problems finding .357 ammo, though.