Why the 15-inch gun remained the practical choice

If treaty limits disappeared, would an 18-inch gun be preferable to a 15-inch weapon?

No. The 18-inch gun offered more power, but its heavy turret and structural demands made the 15-inch weapon more practical.

Removing treaty limits would not make the 18-inch gun the preferred choice. The weapon offered great power, but its turret was exceptionally heavy and difficult to move. That weight imposed substantial stress on the ship. A 15-inch gun offered a more practical balance between striking power and the demands placed on the hull.