I've hunted with the following, in the mountains of Washington and Idaho. My comments about each are included.
Leupold compact 2x7x28 (on a .280 Remington): Worked great. Hardly there. Loved it. If you have a short-action rifle, or a long action with a 1-piece scope base, look hard at this one.
Leupold 3x9x40 (on a 30-06): Just fine, no complaints, magnification at high end of scale is plenty (possibly too much), scope is physically large - would prefer smaller.
Leupold 6x42 (on a 30-06): keep it simple stupid magnification, works great for deer rifle in open mountainous country, a little much magnification for in the woods but not impossible. 42mm objective is physically large, would prefer smaller for carrying in mountains.
Leupold 1.5x5x20 (on a 300 Win): Very light, good optics, absolutely outstanding in timber, great to carry with straight-tube objective. Some may want greater magnification, but not mandatory in my book.
Leupold 2.5x8x36 (on a 300 win): Great balance between magnification and size/weight. I wouldn't want larger.
I have divested myself of all my scopes with objective larger than 40mm. They just don't make sense for how I hunt.
My conclusion is simple:
1. If you expect to get your animal back to your truck in one piece, wear no pack or a daypack while hunting, carry less than a quart of water with you, consider Schnee's to be good hunting boots, or wear cotton, get whatever turns your crank.
2. If it's coming in chunks with bones attached, you hunt with a daypack, and carry less than 2 quarts of water, set a maximum of 40mm objective.
3. If it's coming out with no bones attached (except for the skull cap), you hunt with a substantial pack or packframe, carry more than 2 quarts of water, spend over an hour in the morning darkness hiking hard, or hunt from / are packed in by a horse, seriously consider a straight tube or a compact scope.
And, to piss off all of the fans of huge magnification, there is absolutely no reasonable circumstance in which you need more than 6x, regardless of whether you have the marksmanship capability of shooting past 300 yards.
Stay light, hunt happy.