When two boats share the same hull type — in this case both the Zodiac Medline 580 2013 and the Zodiac Pro Racing 550 2013 are deep vee designs with rigid inflatable 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?

On paper these two are close siblings in the size department — Zodiac Medline 580 2013 at 19,0 ft versus Zodiac Pro Racing 550 2013 at 17,1 ft. Weight tells a clearer story for trailering families: the Zodiac Medline 580 2013 tips the scales at 1 325 lbs — 631 lbs more than the Zodiac Pro Racing 550 2013 at 694 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.

Both boats share a closely matched power ceiling — 80 hp for the Zodiac Medline 580 2013 and 90 hp for the Zodiac Pro Racing 550 2013. Real-world performance will come down more to which motor is actually bolted on, its load at the time, and whether it's a 4-stroke or 2-stroke setup.

Both boats are rated for 12 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.

At this size, power-to-weight ratio matters more than outright horsepower. The Zodiac Pro Racing 550 2013 comes in at 8 lbs per hp versus 17 lbs per hp for the Zodiac Medline 580 2013. The lower the ratio the more explosive the acceleration — meaningful on a short RIB where bursts of speed, quick planing, and agility in surf or tight waterways define the experience.

The Zodiac Pro Racing 550 2013 has a documented top speed of 42 mph. Speed data wasn't available for the other model.

Both are inflatable designs, which means they pack down for compact storage, can be carried in a bag, and are dramatically lighter than equivalent rigid hulls. The trade-off is setup time and the need to monitor tube pressure regularly. Tube diameter differs: 1 ft. 10 in. (0.55 m) on the Zodiac Medline 580 2013 vs 1 ft. 8 in. (0.5 m) on the Zodiac Pro Racing 550 2013 — larger tubes generally mean more buoyancy and a drier, more stable ride.