It sounds as though you have two ideas in mind to select from. Either the 3x9 or the 4x12. The one power range difference on the lower end is not going to have an great effect on you finding a coyote at 30 yards. That is a matter of getting used to acquiring a target on the move in close. There is no tremendsous gain in being one power lower at 30 yards. The three power range difference on the top end(9X as opposed to 12X) will indeed make a difference on smaller targets or targets at extended range. If brightness during low light is a concern(you mentioned) then increase your objective size to a 50mm.
You say you are new at this predator game. Well the objective of calling is to get them to come to you, the closer the better. Keep the scope set on the lower power. If they hang up out there you will have time to increase power, not vice versa if they surprise you in close.
All this being said, my calling rifles all wear VX-III 4.5x14x50. Any new scope purchases lately though, I've shy'd away from the Leupold to the upper end Bushnells such as the 4200 and the 3200, great quality, yet at least two hundred dollars less. You will buy upper end Bushnells almost for what you pay for the VX-II's.
