When two boats share the same hull type — in this case both the Zodiac Pro Open 550 2008 and the Zodiac Zoom 310 SR 2008 are inflatable rigid 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?

Size is the most obvious dividing line here. The Zodiac Pro Open 550 2008 measures 18,0 feet overall (2008), giving it roughly 17,0 additional feet of deck space compared to the Zodiac Zoom 310 SR 2008 at 1,0 feet (2008). At 97 lbs and 93 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 120 hp, the Zodiac Pro Open 550 2008 has a 112-hp advantage over the Zodiac Zoom 310 SR 2008's 8-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 Open 550 2008 is rated for 11 passengers, while the Zodiac Zoom 310 SR 2008 caps at 4. If you're regularly pulling extended family or a group of friends onto the water, the extra seats on the Zodiac Pro Open 550 2008 could be the deciding factor.

At this size, power-to-weight ratio matters more than outright horsepower. The Zodiac Pro Open 550 2008 comes in at 1 lbs per hp versus 12 lbs per hp for the Zodiac Zoom 310 SR 2008. 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 Open 550 2008 has a documented top speed of 45 mph. Speed data wasn't available for the other model.