What is the Revolver's mission?
Will you be running mainly factory-level loads (250gr. @ 850 f/s) through the revolver, or do you anticipate the use of more powerful loads on a regular basis? The S&W's action is likely more "tuneable" to give you best accuracy, but may not stand up to a steady diet of heavier loads. The Redhawk's action is less amenable to tuning, but is somewhat more robust, so regular use of more emphatic loads is unlikely to loosen it as rapidly or as much.
I'm not sure that the S&W can be made to shoot twice as accurately as the Redhawk. I'm pretty certain that the Redhawk will tolerate higher pressure loads twice as long (or more) as the S&W. All factors being equal, I'd probably go with the Redhawk, but I might regret the decision later.