I prefer the head-ball break. Since my goal is to break and run out, I simply want the most spread out rack to accomplish the task. Although people argue that if they don't make a ball on the break, they don't want to leave an easy rack for their opponent. However, when I analyzed our final league stats, there is nobody running out more than 10 racks out of 78 games in the season, and the highest this year is 7 table runs.
I know good players that prefer the second ball break. Their theory is that they feel that they have a better shot at running out a rack with clusters than their opponent. The problem is, see above. Nobody in our league runs out an extremely high percentage of racks. So really, this isn't a valid argument.
And for those claiming that they can make the 8 ball on the break 8% to 10% of the time. I say that's an exaggeration. Out of 78 total games in our league, a player will break 1 or 2 times a night out of 3 total games. So an exact percentage is not possible, but two 8-ball breaks is around 5.2% for those with the most number of 8-ball breaks (2 or 3 at the end of the league).