Well, the sp101 is a great gun. I have one. It is very accurate with the right ammo. But if you are going to use this gun just for deer hunting I suggest you look into the ruger gp100. They offer a nice .357 wheelgun with the option for a longer barrel than the sp101(6inches). But if I had to pick one of barrel lengths you mentioned I would take the 4.2.
Everybody needs a little Devastation!