The choice depends entirely on your finish requirements and material thickness. Up-cut bits are best for rapid chip removal and deep mortising, but they may cause splintering on the top surface. Down-cut bits push chips downward, providing a clean top edge, making them ideal for thin materials or shallow grooves. For double-sided laminates or plywood, Compression bits are the professional choice as they pull fibers toward the center from both top and bottom, ensuring a burr-free finish on both sides.