the 586 and 686 were created to fulfill a niche that was created by new training programs that sprung up in the 80's. Prior to then, most depts. trained with 38's and then maybe shot a cylinder full of 357 mags, but some lawsuits came up and depts decided to train with what they carried.
When a model 19 is shot all the time with full house 357 mags, the gun gets loose, the forcing cone gets shot out and there can be some stretching in the top strap. The x86 L frame models were developed to live on a steady diet of 357 mag loads. The 86 models all came with fully lugged barrels at first too, as it was considered that the weight of the lug forward not only helped make recoil more managable, but helped keep the recoil impulse from shaking the gun out of time.