The Duckworth 215 2011 is a deep-V design and the Duckworth 721 2010 is a modified-V design, so you're likely deciding between two noticeably different on-water experiences. Hull type shapes everything from ride quality and fuel burn to dock handling and resale trajectory.
On paper these two are close siblings in the size department - Duckworth 215 2011 at 21,5 ft versus Duckworth 721 2010 at 21,0 ft. Weight tells a clearer story for trailering families: the Duckworth 215 2011 tips the scales at 2 270 lbs - 670 lbs more than the Duckworth 721 2010 at 1 600 lbs. That difference is meaningful if you're working within a half-ton or three-quarter-ton truck's tow rating, especially once you factor in a motor, gear, and fuel.
The power gap is worth calling out. Rated to 250 hp, the Duckworth 215 2011 has a 50-hp advantage over the Duckworth 721 2010's 200-hp ceiling - enough to notice on acceleration and at cruising speed, particularly with a full passenger load. Fuel capacity breaks the other way: the Duckworth 215 2011 carries 62 gallons versus 42 gallons in the Duckworth 721 2010. On a lake day that's negligible, but for coastal cruising or long reservoir runs the extra range matters.
Both boats are rated for 6 passengers - a good fit for a family of four or five plus guests. Comfort at capacity is another matter; the longer hull typically means more seat options and better weight distribution.
Bottom line: Performance buyers should lean toward the Duckworth 215 2011 and its 250-hp ceiling. If fuel economy and quieter running matter more than top-end speed, the Duckworth 721 2010 with its 200-hp rating is the more economical daily driver.