Depending on what you are planning to do with the rifle, the 325 may or may not offer you more power then the 300 WSM
For closer range shooting it will offer more dramatic terminal effects then the smaller caliber 300. By that I mean the heavier, larger diameter bullets will have more effect on heavy game at close to moderate ranges.
Because of the better BC of most 30 cal bullet though, at longer range the 300 will have an advantage in retained velocity, energy and with same bullet design, they generally penetrate deeper as well.
Again, it depends on the range you will be using and also on what type of critters will be hunted.