The longer the barrel the longer the sight radius, the easier to hold on target. The longer barrel the less felt recoil, muzzle heavy (longer) guns don't flip (rise) as much. Also you will get less muzzle flash from the longer barrel and that's a real plus indoors. So for a range gun I'd go 6" every time. For carry go 4"

Joe, I would suggest going to a local store and see how each feels in your hand. Which ever one you feel is more balanced to you is the one I would go with. True the longer barrel pistol with more weight will soak up some of the recoil but it's not going to be a night and day difference in recoil, just slightly more perceived muzzle blast. The longer sight radius will help with longer distance shooting and the longer barrel will increase velocity given the same ammunition. Once you handle the two, you will know which you prefer.