The boreline axis-to-cylinder axis is greater on the L frame than on the K frame.
The barrel shank ("forcing cone") end of the barrel is thicker on the L frame than the K frame.
The cylinders are obviously different diameters, with more material between chambers on the L frame than the K frame.
For comparison purposes, the L frame is comparable to the Colt 41 frame size of the Python and Trooper series.