When two boats share the same hull type — in this case both the Duckworth 21 2010 and the Duckworth Ultra Magnum Inboard 24 ft. 2008 are deep vee designs with aluminum construction — the buying decision usually comes down to a handful of practical questions: how many people are you putting on the water, how far do you trailer, and what does your tow vehicle weigh?
On paper these two are close siblings in the size department — Duckworth 21 2010 at 21,0 ft versus Duckworth Ultra Magnum Inboard 24 ft. 2008 at 24,0 ft. Weight tells a clearer story for trailering families: the Duckworth Ultra Magnum Inboard 24 ft. 2008 tips the scales at 372 lbs — 344 lbs less than the Duckworth 21 2010 at 28 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.
For family outings this is probably the sharpest distinction between the two. The Duckworth Ultra Magnum Inboard 24 ft. 2008 is rated for 7 passengers, while the Duckworth 21 2010 caps at 6. If you're regularly pulling extended family or a group of friends onto the water, the extra seats on the Duckworth Ultra Magnum Inboard 24 ft. 2008 could be the deciding factor.
Bottom line: Choose the Duckworth Ultra Magnum Inboard 24 ft. 2008 if your priority is putting more people on the water — it handles 7 passengers and at 24,0 ft it has the deck room to back that rating up comfortably. The Duckworth 21 2010 is the smarter pick if you want a lighter, easier-to-trailer boat rated for 6 that costs less to run day-to-day.