Both the Mariah R23 2012 and the Mariah SX21 2010 are modified-V designs, the first built in aluminium and the second in fibreglass, so 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 - Mariah R23 2012 at 23,4 ft versus Mariah SX21 2010 at 20,8 ft. Weight tells a clearer story for trailering families: the Mariah R23 2012 tips the scales at 4 000 lbs - 400 lbs more than the Mariah SX21 2010 at 3 600 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 320 hp, the Mariah R23 2012 has a 50-hp advantage over the Mariah SX21 2010's 270-hp ceiling - enough to notice on acceleration and at cruising speed, particularly with a full passenger load. Fuel capacity breaks the other way: the Mariah R23 2012 carries 52 gallons versus 44 gallons in the Mariah SX21 2010. 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 Mariah R23 2012 is rated for 12 passengers, while the Mariah SX21 2010 caps at 10. If you're regularly pulling extended family or a group of friends onto the water, the extra seats on the Mariah R23 2012 could be the deciding factor.
Bottom line: Choose the Mariah R23 2012 if your priority is putting more people on the water - it handles 12 passengers and at 23,4 ft it has the deck room to back that rating up comfortably. The Mariah SX21 2010 is the smarter pick if you want a lighter, easier-to-trailer boat rated for 10 that costs less to run day-to-day.