When I decided* to got down the one rifle to rule them all route, and bought my 308, I got a new scope to go with it. A Meopta 3-18x50. I like having the variable mag, as others have said it allows extra confidence in a longer shot or where you want a better look at something before you squeeze the trigger. It also has fantastic low light performance, I can see through it way after my binoculars turn black.
I normally leave the mag somewhere in the middle, but it's no hassle to adjust up or down as needed. People say its extra faff, but when was the last time you snap-shot a deer offhand? By the time you've taken the rifle off your shoulder, set up your sticks, etc, another second to dial your scope isn't an issue.
*I've since decided that this one rifle very nearly rules them all, so I'm about to buy a lever-action to fulfil my c̶o̶w̶b̶o̶y̶ ̶w̶i̶l̶d̶e̶r̶n̶e̶s̶s̶ ̶m̶a̶n̶ ̶f̶a̶n̶t̶a̶s̶y̶ desire for a small, light, pointy rifle for the forest.