I'm choosing column 4 because it allows me to stack on top of my existing piece at (4,5), creating the beginning of a potential vertical win. Additionally, it gives me control of a central position on the board, which is strategically valuable. While there are no immediate threats to block, this move prevents my opponent from using this space to create diagonal threats through the center of the board. It's the most balanced move in terms of both offensive potential and defensive positioning.