I use a Bushnell 3.5-21X for long range ballistics work and never set it above 15X when taking shots at 900-1200 yds. Having more magnification is handy at the range when milling misses.
When hunting, however, I almost never go above 16X. One of my favorite hunting scopes is a Swarovski Z5 3.5-18x44. The BRH reticle has mrad holdoffs at 18X. It has IPHY holdoffs at 16X. Usually, I either set it to 9X or 18X (when holding off in mrad at the range), or 8X or 16X (when holding off in IPHY when hunting). I also use 4.5-15X scopes for long range shooting, and 15X works very well at ranges up to 1,000 yds.
I've also been interested in the Swarovski Z5s, based on price, weight and the excellent glass. I wish they made the 3.5-18x with a 50mm objective for the additional light transmission on the higher powers. Last I knew, the only option was 44mm.
Who makes the 4.5-15x power range? I mostly only see 4.5-14x.