Hi Irv, Sorry, I can't help with any words of wisdom about the Precision 21s. Have never seen one, and know nothing about them. Montgomerys are well built: no oil canning of the hull in the bow area in a seaway; no soft decks; excellent design by a knowledgeable sailor who knows what is important and provides it: ......like good sail lockers and storage space; good cockpit layout; and for the helmsman, good visibility. As you go up in boat length, the volume goes up as a cube function. An M17 is a MUCH larger boat than is the M15, and the Precision 21 would be that much larger again. ......but: then you are into stepping a much longer and heavier mast; probably need a bigger tow vehicle; the boat probably has a greater draft, which limits your sailing areas and the ramps you can use; .....and the complications of a larger boat keep adding up. Connie