Re: S&W MODEL 41
I am surprised you were able to find new ones. Most model 41 were already sold before they hit the dealers floor. Maybe S&W has restarted production (???).
The 5.5 inch version is better for mounting a red dot and the 7 inch one better for open sight shooting because the sight radius is longer with the longer barrel. I think the balance in the hand is better with the 5.5 inch barrel. There is no measurable difference in the accuracy between the two.
I have the 7 inch version and a Clark 5.5 inch barrel for it with a red dot (UltraDot one inch) mounted. I, of course, prefer the red dot version as it can produce better result because of the increase in sighting accuracy with most full sized red dots.
Have fun with whatever Model 41 you happen to choose. They are superb guns! After the Model 41 you will need to get a Connecticut made High Standard.