Both the Triton Boats 20HP Pro 2009 and the Triton Boats 21X3 Pro SC 2009 are modified-V designs, both built 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?
The power gap is worth calling out. Rated to 300 hp, the Triton Boats 21X3 Pro SC 2009 has a 50-hp advantage over the Triton Boats 20HP Pro 2009's 250-hp ceiling - enough to notice on acceleration and at cruising speed, particularly with a full passenger load. Both carry nearly identical fuel loads - 54 gal and 53 gal - so range won't be a tiebreaker here.
Both boats are rated for 6 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 Triton Boats 21X3 Pro SC 2009 and its 300-hp ceiling. If fuel economy and quieter running matter more than top-end speed, the Triton Boats 20HP Pro 2009 with its 250-hp rating is the more economical daily driver.