Both the Mariah R18 2011 and the Mariah RX181 Bow Rider 2008 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 R18 2011 at 18,3 ft versus Mariah RX181 Bow Rider 2008 at 18,0 ft. Weight tells a clearer story for trailering families: the Mariah R18 2011 tips the scales at 3 300 lbs - 850 lbs more than the Mariah RX181 Bow Rider 2008 at 2 450 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 225 hp, the Mariah R18 2011 has a 35-hp advantage over the Mariah RX181 Bow Rider 2008's 190-hp ceiling - enough to notice on acceleration and at cruising speed, particularly with a full passenger load. Both carry nearly identical fuel loads - 22 gal and 22 gal - so range won't be a tiebreaker here.
Both boats are rated for 8 passengers - a good fit for a family of four or five plus guests. Comfort at capacity is another matter; the longer hull typically means more seat options and better weight distribution.
Bottom line: Performance buyers should lean toward the Mariah R18 2011 and its 225-hp ceiling. If fuel economy and quieter running matter more than top-end speed, the Mariah RX181 Bow Rider 2008 with its 190-hp rating is the more economical daily driver.