The Starcraft Marine Nexstar 2100 I/O 2006 vs Starcraft Marine STX 186 Viper 2011 comparison sits squarely in the category of decisions where specs alone won't tell the whole story — intended use, storage, and long-term ownership costs all factor in.
On paper these two are close siblings in the size department — Starcraft Marine Nexstar 2100 I/O 2006 at 21,0 ft versus Starcraft Marine STX 186 Viper 2011 at 18,0 ft. Weight tells a clearer story for trailering families: the Starcraft Marine STX 186 Viper 2011 tips the scales at 1 333 lbs — 1 310 lbs less than the Starcraft Marine Nexstar 2100 I/O 2006 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 175 hp, the Starcraft Marine STX 186 Viper 2011 has a 169-hp advantage over the Starcraft Marine Nexstar 2100 I/O 2006's 6-hp ceiling — enough to notice on acceleration and at cruising speed, particularly with a full passenger load. Both carry nearly identical fuel loads — 45 gal and 43 gal — so range won't be a tiebreaker here.
For family outings this is probably the sharpest distinction between the two. The Starcraft Marine Nexstar 2100 I/O 2006 is rated for 12 passengers, while the Starcraft Marine STX 186 Viper 2011 caps at 6. If you're regularly pulling extended family or a group of friends onto the water, the extra seats on the Starcraft Marine Nexstar 2100 I/O 2006 could be the deciding factor.
Bottom line: Choose the Starcraft Marine Nexstar 2100 I/O 2006 if your priority is putting more people on the water — it handles 12 passengers and at 21,0 ft it has the deck room to back that rating up comfortably. The Starcraft Marine STX 186 Viper 2011 is the smarter pick if you want a lighter, easier-to-trailer boat rated for 6 that costs less to run day-to-day.