Wrong Question to Ask...
This question is moot..
If you carry people, people that sign your paycheck, they will not appreciate a dive bomb approach, steep deck angles, rapid decents, ect...fly like that too much, and your looking for a new job pretty soon..
That said...you can fly around with 50% power all day long and call it 'efficient' because your saving fuel...others will counter that your burning up engine time...everyone will have thier calculators out, then start arguing seat per nautical mile, compare the cost per trips on the airlines...and I have known guys that can work the numbers right to get anyone to consider a GIV by the time they are done...
Last I remember we are all trying to get from Point A to Point B. safely..he who get's there the fastest wins...he who get's there the fastest and most comfortable really wins...and he who get's there the fastest, most comfortable and for the least amount of money, really, super duper wins...
So in your plane, which type of decent profile, will obtain all these objectives...
Usually a nice normal decent, as fast as you can go, in such a way that's safe, and comfortable for the passengers...