45 Colt would be my choice. It should be the lightest of the 3 calibers (if weight is a concern) and since you reload, you can really have a wide range of power levels.
I have a 41 mag in a model 57 smith with a 4" barrel and a Blackhawk in 45 colt with a 4 5/8" barrel. I find top end loads much more pleasant to shoot in the Ruger than in the Smith.
I don't think you would go wrong with any of the 3 calibers.
