As a player devolopment instructor I have a lot of experience with players getting frustrated with their hitting mechanics. What I notice  is that their mechanics are good, but they are not in rythem and time with their load and stride. When hitters do not get down and flat with their front foot on time they will essentially unlock out of sequence causing thier mechanics to break down. When coaching hitters be sure to check timing before adjusting mechanics.

 The answer is neither, and let me explain. When I'm working with kids at the facility I want them to focus on their contact point.  It does not matter where or what the pitch is. The main focus should be making contact at the hitters strong point. The strong point is where the hitter feels strongest at the point of contact. If this is taking place on a consistent bases the result will be more often a success rather than a failure. So the answer to the question is with a strong contact point average and power will take care of it's self.