Whether or not I would use the power in this question would depend on the process that is used to determine which 1% of humanity would live, and which 99% would die.  Here's how I would respond to several case scenarios:

If the 1% and 99% are chosen completely at random with no other outside inputs, I would not use the power because of the potential that utterly corrupt people and their progeny would have the opportunity to help shape this "great future", when the "great future" could be even better if more worthy people were involved in it.

If there is a known and well-defined, merit-based algorithm that would be the sole arbiter of determining who lives and who dies, then I would look at that algorithm to see if I agree or disagree with the standards that are used to determine merit.  If I agree with those standards, then I would use the power without hesitation, and without regard to if I was in the 1% or 99%, because I can be assured that the absolute best people would shape the best future paradise possible.  If I disagree with those standards, then I would not use the power.

If I was the sole arbiter for determining who would live and who would die, I probably would not use the power for this reason: Earth's population is around 7.5 billion people.  1% is 75 million people, and I sure haven't met anywhere near 75 million people.  If I added all the people I ever met and all the living people that I've ever read or heard about, that still wouldn't get me anywhere near 75 million people.  The number of spots for the living that I would have to fill would simply be too great, and most of those spots would be filled based on an utter lack of information as to who might be worthy or not of living (i.e. complete ignorance on my part).

The ideal scenario for me would be if I could choose a limited number of people to protect (i.e. guarantee their lives and their participation in shaping the future paradise), choose a limited number of people to kill off, and let a merit-based algorithm that I agree with take care of the rest.  That would mean that the people I care for and who understand what would be happening and why, would get to continue living under continually improving circumstances, and the best of humanity would also get to enjoy these benefits.  The resulting future may not be as perfect as letting a merit-based algorithm do all the work (because I could end up protecting some people who would be part of the 99%), but it would be acceptable enough for me.