When going the caulk route, it's important to follow the manufacturer's specs for filler strips. You can't just fill a huge void with caulk and walk away. If it's over a certain width/depth (usually 3/8"-1/2" max), you need to put those foam backer rods in the space, under the caulk. Too many people neglect this important step, then blame the caulk for failing. Caulk expands and contracts like an accordion. It can only be adhered on 2 opposite sides. If it's adhered to 3 adjacent sides, it will pull away from one, opening up a gap. Even if it's applied to 2 sides, properly, if the gap is wider than the manufacturer's specs it will either crack in the middle or pull away from one side.