If you are not planning of shooting magnums (and I can think several good reasons not), I can think of several good reasons for buying a .38 Special only revolver.There is no reason to buy a ".38 Spcl" only gun unless you need a lightweight snub for concealed carry.
1. A K-frame is still K-frame (M10/13/64/66). A heavy barrel is a heavy barrel. You definitely lose in the weight arena when you move up to a L-frame (weighs more than a N-frame for the same barrel length).Yes, it's still magnum and it has a heavier barrel and frame which reduces the chances of the gun failing. If the price is almost the same (and weight) it makes sense to get the magnum and be able to shoot any load you want.