This study examines the necessity and benefits of the three-dimensional synthetic aperture focusing technique (3D SAFT) compared to the two-dimensional SAFT (2D SAFT) used in ultrasonic nondestructive testing. Using a point flaw and an oblique plane reflector as test cases, the image quality improvement of 3D SAFT over 2D SAFT is quantified. Results show that 3D SAFT requires higher cost and longer scanning and processing times than 2D SAFT, but it provides superior image quality and more accurate reconstruction of flaw position and shape. When high-resolution imaging and reliable geometric interpretation are required, and time and cost are not limiting factors, 3D SAFT is preferred. When efficiency and cost are priorities, 2D SAFT offers a practical alternative. However, the scan direction needs to be perpendicular to the target orientation. Therefore, the choice between 2D and 3D SAFTs involves a trade-off among image quality, time, and cost.