Too many variables for a
definitive answer.

Revolver chambers vary;
in the good old target days
with revolvers competitors
often marked their chambers
as to which shot the best with
their given handloads. Not
uncommon that one chamber
or two weren't as good as the
others. Or visa versa.

Ditto in comparing not only the
many possibilities in factory and
handloads but different chamber
oddities from .38 to .357 revolvers.

And let's not forget cylinder gap
variations and forcing cone variations.
Or even variations from one production
run to another for barrel riflings.

I'd say that sticking to .38s for .38
chambers only at least eliminates
some of the variables that would
come into play with using .357
chambers.

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