I've always been a supporter of the line drive or "hitting the middle half of the ball". A couple years ago I spent time watching MLB games charting swings in a completely unscientific (feet up with a beer, clip board and pencil) study. My criteria were simply: was the swing under the ball (including complete misses, pop ups, fly balls most home runs etc), on top of the ball (again complete misses, fouls, ground balls foul and ground balls fair) or in the middle of the ball (line drives). After several games the results showed 60% of swings were under the ball. The remaining 40% was pretty evenly split between on top and in the middle.
An extreme example came during a Brewers game. The first batter of the inning steps up and his first swing results in a pop foul out of play. His next swing is a repeat. 3rd swing the same and his 4th swing results in yet another pop foul only this is playable and caught by the catcher. 4 swings all under the ball resulting in an out. The next guy comes up and essentially does the same thing only he pops the the ball up on 5 straight swings resulting in an out when the 5th pop foul was also caught by the catcher. The numbers: 2 batters. 9 swings. 9 pop fouls. 2 outs.
I thought about this and came away with the following. The balls were at different heights during swings and yet these guys were good enough to consistently swing "under" the ball. So my question was if they are skilled enough to make that adjustment why can't they make another adjustment and hit the ball consistently in the middle? Or are they so dialed in that hitting under for them was automatic?
Again, theses 2 guys are an extreme example but interesting to say the least.
remember the pitcher has something to say about this too. Were the pitchers high velocity? High rpm guys? Read up on spin rates on fastballs. Fascinating stuff.