Grind and Seal Versus True Mechanical Polish
Grind and seal grinds the surface lightly, then applies a topical sealer for shine. It is cheaper, but the sealer wears and needs reapplying.
True mechanical polish progresses from metal-bonded diamonds to resin-bonded diamonds, often up to 800, 1500 or 3000 grit. The gloss is in the concrete and lasts.