When two boats share the same hull type — in this case both the Zodiac Medline 500 2013 and the Zodiac Pro Classic 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 500 2013 at 16,4 ft versus Zodiac Pro Classic 550 2013 at 17,1 ft. At 778 lbs and 694 lbs respectively, both sit in a similar weight class — either should pair comfortably with most mid-size SUVs and half-ton trucks, though always confirm your specific tow rating with the motor added.
The power gap is worth calling out. Rated to 90 hp, the Zodiac Pro Classic 550 2013 has a 50-hp advantage over the Zodiac Medline 500 2013's 40-hp ceiling — enough to notice on acceleration and at cruising speed, particularly with a full passenger load.
For family outings this is probably the sharpest distinction between the two. The Zodiac Pro Classic 550 2013 is rated for 12 passengers, while the Zodiac Medline 500 2013 caps at 9. If you're regularly pulling extended family or a group of friends onto the water, the extra seats on the Zodiac Pro Classic 550 2013 could be the deciding factor.
At this size, power-to-weight ratio matters more than outright horsepower. The Zodiac Pro Classic 550 2013 comes in at 8 lbs per hp versus 19 lbs per hp for the Zodiac Medline 500 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 Classic 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.
Bottom line: Choose the Zodiac Pro Classic 550 2013 if your priority is putting more people on the water — it handles 12 passengers and at 17,1 ft it has the deck room to back that rating up comfortably. The Zodiac Medline 500 2013 is the smarter pick if you want a lighter, easier-to-trailer boat rated for 9 that costs less to run day-to-day.