The L frames (586, 686) are almost the same size through the cylinder and frame, they just used the smaller grip of the K frame ( model 10, 19, etc.),and a very slightly smaller cylinder and frame.
The guns are close enough that many holsters will work with either frame size.
Some grips are big,even on the K and L frames, but with the assortment of revolver grips available almost anyone can find a grip they can use on an N- frame.
As to weight. The 27 with it's thinner barrel and shorter ejector shroud is actually lighter than the 586/686.