When two boats share the same hull type — in this case both the Sundance NX21 2012 and the Sundance SV23 2008 are modified vee designs with fiberglass 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 — Sundance NX21 2012 at 21,1 ft versus Sundance SV23 2008 at 23,0 ft. Weight tells a clearer story for trailering families: the Sundance NX21 2012 tips the scales at 185 lbs — 162 lbs more than the Sundance SV23 2008 at 23 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 Sundance SV23 2008 has a 100-hp advantage over the Sundance NX21 2012's 150-hp ceiling — enough to notice on acceleration and at cruising speed, particularly with a full passenger load. Fuel capacity breaks the other way: the Sundance SV23 2008 carries 72 gallons versus 45 gallons in the Sundance NX21 2012. On a lake day that's negligible, but for coastal cruising or long reservoir runs the extra range matters.
For family outings this is probably the sharpest distinction between the two. The Sundance NX21 2012 is rated for 8 passengers, while the Sundance SV23 2008 caps at 7. If you're regularly pulling extended family or a group of friends onto the water, the extra seats on the Sundance NX21 2012 could be the deciding factor.
Bottom line: Choose the Sundance NX21 2012 if your priority is putting more people on the water — it handles 8 passengers and at 21,1 ft it has the deck room to back that rating up comfortably. The Sundance SV23 2008 is the smarter pick if you want a lighter, easier-to-trailer boat rated for 7 that costs less to run day-to-day.