Column 4 is the best strategic choice for several reasons:
1. Defense: My opponent has two X pieces stacked in column 4. While not an immediate threat, it's worth blocking a potential vertical build-up.
2. Offense: Placing my piece here extends my horizontal presence from columns 2-3 into column 4, creating more opportunities for future connections.
3. Center control: Column 4 provides good board control, as the center columns generally offer more connection possibilities.
4. No disadvantage: This move doesn't create any obvious opportunities for my opponent, as I'm not setting up any "connect 3" situations that could be completed from above.