For me, the FA square butt rides in the heel of my palm, giving more support when I handle the gun. I have also tested this with 2 friends firing Model 83's in .454, alternating a square butt gun with a round butt gun, and came away with the same conclusion, much preferring the square butt. One of my friends agreed completely, while the other noted no real difference for him.
This is a very personal thing, and opinions vary. Your best option is to try to handle both, then form your own opinion. Even FA does not recommend round butts on guns with barrel lengths longer than 6", FWIW, but I know that Bob Baker likes them on short barrel guns.
How one or the other feels to me has nothing to do with how it will feel for you.
