Matching a modified vee Duckworth 721 2010 against a deep vee Duckworth Navigator Sport 18 2013 means you're likely deciding between two genuinely 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 721 2010 at 21,0 ft versus Duckworth Navigator Sport 18 2013 at 18,3 ft. Weight tells a clearer story for trailering families: the Duckworth Navigator Sport 18 2013 tips the scales at 142 lbs — 126 lbs less than the Duckworth 721 2010 at 16 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 200 hp, the Duckworth 721 2010 has a 85-hp advantage over the Duckworth Navigator Sport 18 2013's 115-hp ceiling — enough to notice on acceleration and at cruising speed, particularly with a full passenger load. Both carry nearly identical fuel loads — 42 gal and 42 gal — so range won't be a tiebreaker here.
For family outings this is probably the sharpest distinction between the two. The Duckworth 721 2010 is rated for 6 passengers, while the Duckworth Navigator Sport 18 2013 caps at 5. If you're regularly pulling extended family or a group of friends onto the water, the extra seats on the Duckworth 721 2010 could be the deciding factor.
Bottom line: Choose the Duckworth 721 2010 if your priority is putting more people on the water — it handles 6 passengers and at 21,0 ft it has the deck room to back that rating up comfortably. The Duckworth Navigator Sport 18 2013 is the smarter pick if you want a lighter, easier-to-trailer boat rated for 5 that costs less to run day-to-day.