How much does gun weight and barrel length factor into this?
Quite a bit. The .357 magnum really needs a 4" barrel or longer to gain it's full potential, which is why I stick to .38+p in snubs. As far as weight, the airweight .357 snubs are novelty pieces to me, they are just not practical. I can put more .38 special rounds on target faster and more accurately out of a snub than I can with a .357 round in the same gun. The slight edge you gain with 100-200fps faster does not make up for that, for me at least.