The only reliable way to test accuracy is to shoot groups on paper targets and compare them. This is best done on a bench, with a front rest and rear sandbag or from whatever will be most steady. Use the highest power scope you can. 2-3 three shot groups at 200 yards would be best to test both accuracy and conserve that expensive ammo. You may need to briefly shoot at 100 to sight in first. You will do fine with a 150 gr. bullet. Would a 168 or heavier bullet be better? Again the only way to tell is target shooting at paper. Both will kill any deer, elk probably, moose iffy, black bear probably, grizzley bear not advised (see .375 H&H).