When comparing the many 30 cal cartridges, I find it helpful to put it in terms of range.
A 308 at 100 yards is about equal to a 300 win mag at 300 yards. Shooting the same 165 or 180 grain bullet, the velocity and energy of the 308 at 100 yards is pretty much equal to the magnum at 300 yards. So from a "power" standpoint, the 300 win mag is like being 200 yards closer to your target.
Traditionally, hunters in open country liked high velocity cartridges (above 3000 fps) because it maximized the so-called point blank range... that is the range at which no hold-over is required. But a lot of hunters today use a range finder, and click off elevation changes on their scope, in which case cartridges in the 2600 - 2800 fps range, like the 308, will get the job done.