It all kind of depends on the size of the game, how fast the game is expected to move (considering the shooter is good at bagging fast-moving targets), the ultimate range, mirage concerns, etc.
I require no more than 14X at the top end for closer very small targets such as ground squirrels with a .22 rimfire, although I have used an old Tasco Custom Shop 8 x 40 scope on my .222 and .22 rifles. But....the 8 x 40 on the bench rest .222 makes the rifle weigh a ton.....but no problem because it is used as a BR rifle only, whereas I want the rimfires to be "carryable" as well as being used off the bench.
It just depends on a lot of things. I just ordered an inexpensive Simmons 6 x 18 Pro Hunter with a side-focus to try it out for rimfire shooting, where the ranges are all over the map for ground squirrels, and I found that I was constantly twisting the adjustable objectives on the end of my existing scopes. The Tasco has a huge side-focus knob that makes it easy to adjust. I found that I rarely use the 40X power, but at the time I purchased this monster, there were no other scopes available in the price range that had the side-focus feature. The scope has about a 60mm objective lens with a 30mm tube. The biggest disadvantage is the size and weight of the scope.
For long-range shooting, I found little difference between 20X and 24X in the past. I like to use the high power for sight-in because I am too lazy to drag out the spotting scope.
For wild pigs and coyotes I use a 1.5 x 5 Leupold Vari-X III since I have found that these animals often are encountered at close range and are large enough to not really require anything more powerful. Also, the scope is very light when mounted on my .270 Remington Mountain Rifle, and back problems tend to limit any future carry-rifle scope choices to ones that are as light as possible.
