You'll get all sorts of thoughts on this. Here are mine...

I do handload using .357 cases and have loads ranging from mild with cast lead bullets, to wild with jacketed bullets. I dont use .38 cases for reloading (though I do shoot a lot of factory .38's), only because I dont want to readjust my dies every time I switch.

There is nothing wrong with using light loads in .357 cases, and a lot of folks would recommend it just to avoid the crud ring that can build up in the chambers from shooting the shorter .38 cases. Personally, I have never felt like this was an issue -- but then I also clean my guns thoroughly every time I shoot them.

An arguement the other way might center around potential accuracy issues with light loads in .357 case compared to a similar load in a .38 case, because of load density and pressure variances. I'd suspect though, that the load and gun will both outshoot the average shooter either way.

FWIW, YMMV.