The only gun I caliber I can think of that fits both USPSA, IDPA and hunting would be the .357mag and I would recommend the GP-100 over the 686 Smith only because if yo go to hunting you want a gun that will take the heavy 357mag loads you will want to use for hunting. Shoot minor in USPSA revolver. The .38spl/.357 mag gun would fit better in IDPA over USPSA. The Rehawk and Super Redhawk are not going to be useful in either USPSA or IDPA. The gun is heavy and big. You are never going to see it in .357 mag. The gun need not be that big and heavy for the ..357Mag.
I agree with the poster who said you are trying to cover to many bases with one gun. For hunting .357 amg is really marginal. 44mag/45colt makes more sense. USPSA now allows 8 rounders I believe in their revolver division so anything with six rounds in it is going to be at a big disadvantage.
Take Care
Bob