I have both the 617-6 4" and 6" 10-shots. If I had to pick one, it would be my 4". It balances and carries better.
I had a 6" 6-shot which I traded for the 6" 10-shot. To me, the 10-shot's a lot more fun to shoot (e.g., Steel Challenge),
especially with DS-10 speedloaders.

Of course, the No Lock versions are more collectable and command a premium. I'd love to find a 4" No Lock 10-shot, SS cylinder.