For deer hunting, I'm sorta negative on a minimum power for a variable of 4X. I prefer 3X or even 2X. Sometimes Bambi gets sorta up close and personal.
And, I have had occasion to take a running shot where field of view is very important.
More opinion: From the standpoint of "need" on Bambi, 4X is plenty good to at least 300 yards, and even 400 if you are sorta "married up" to your gun-package.