The utility sector is changing. An increase in electricity demand is expected to drive faster growth for a sector traditionally seen as a slow-and-steady tortoise. That said, there are different ways to invest in the sector. Some might like historically growth-oriented companies like NextEra Energy (NEE 0.86%), while others may prefer a less exciting business like Black Hills (BKH +0.28%). Here's a comparison of both to help you decide.NextEra Energy is two businesses in oneNextEra Energy owns one of the la ...