When two boats share the same hull type — in this case both the Zodiac Cadet 310 Solid 2013 and the Zodiac Mark I HD 2009 are inflatable non rigid designs with 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?
Both boats share a closely matched power ceiling — 15 hp for the Zodiac Cadet 310 Solid 2013 and 25 hp for the Zodiac Mark I HD 2009. 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 5 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.
The Zodiac Cadet 310 Solid 2013 has a documented top speed of 22 mph. Speed data wasn't available for the other model.
The Zodiac Cadet 310 Solid 2013 is an inflatable design — lighter, easier to store, and quicker to launch from a beach or dock without a slipway. The Zodiac Mark I HD 2009 is a rigid hull, which typically offers a more confident ride in chop and easier maintenance over the long term.
Bottom line: The Zodiac Cadet 310 Solid 2013 and Zodiac Mark I HD 2009 are closely matched on the specs that matter most. Test-ride both on the water you actually use, check current dealer pricing, and factor in long-term service access before you sign.