Pilgrim has the run down as I would have classified it except that if one plans on shooting stout magnum loads the larger framed guns are more durable.

The K framed 19 has a thinned spot under the forcing cone to allow clearance for the crane to close. It has been the experience of many that the use of high pressure rounds with lighter bullets (think 125 grain range) can cause splitting of the model 19 barrels here.

The model 19 was conceived for police officers who wanted magnum power in a gun that was to be carried more than shot (with hot loads) on a regular basis. The difference in carrying a K frame all day as opposed to an N frame is noticeable.