By playing in column 6, my piece will fall to position (6,3), giving me three O pieces in a vertical row (6,3), (6,4), and (6,5). This creates a strong threat that my opponent must block on their next turn, forcing them to respond to my strategy rather than advancing their own. None of the other columns create an immediate threat or block an immediate threat from my opponent. This is a proactive move that gives me the strongest position.