Putting Marv's 1968 model 4 5/8" barrel Mark I next to my 1957 model 6".
It doesn't show very well, but Marv's grips are wood! They are just really heavily used and spent literally decades in the gun cabinet of a friend whose man-cave is also his smoking room.
Personally I think the longer barrel looks better, but your mileage may vary. Of note is the angle of the logo. Apparently mine is the original angle, which looked right to Bill Ruger. Marv's is the later angle which was changed due to customer comments. Not sure that's true or not, but I heard it at a gun shop.