When two boats share the same hull type — in this case both the Key West 177 SK 2009 and the Key West 218 SK 2013 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?
The power gap is worth calling out. Rated to 150 hp, the Key West 218 SK 2013 has a 60-hp advantage over the Key West 177 SK 2009's 90-hp ceiling — enough to notice on acceleration and at cruising speed, particularly with a full passenger load. Fuel capacity breaks the other way: the Key West 177 SK 2009 carries 19 gallons versus 3 gallons in the Key West 218 SK 2013. On a lake day that's negligible, but for coastal cruising or long reservoir runs the extra range matters.
Bottom line: The Key West 218 SK 2013 at 21,0 ft is the right call if deck space, comfort, and entertaining are top of your list. The Key West 177 SK 2009 at 17,0 ft wins on trailering ease, likely lower purchase price, and simpler docking — a solid choice for a buyer who wants more boat for less money.