Buying a gun chambered in .357 mag ...that means you can also shoot .38's in it makes perfectly good sense to me.
The only issue with shooting a lot of .38's in the longer chambers of a .357 mag ...is you'll get some carbon buildup after you shoot the .38's ...and unless you clean the gun thoroughly - that buildup might prevent you from chambering a .357 mag cartridge.
But to me, its no big deal, I clean my guns after every range trip anyway.
Have fun test firing a lot of guns !!
Some of my .357 mag revolvers...
photo isn't great ...but a pair of model 19's 4" Nickel at lower right, a pair of model 66's stainless 4" at upper right ...a model 27 6" blued at left ..and a model 686 6" stainless at upper left...