When two boats share the same hull type — in this case both the Zodiac Cadet Fastroller 310 FR Acti-V INT-L 2008 and the Zodiac Mark II 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?
The power gap is worth calling out. Rated to 50 hp, the Zodiac Mark II HD 2009 has a 40-hp advantage over the Zodiac Cadet Fastroller 310 FR Acti-V INT-L 2008's 10-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 Mark II HD 2009 is rated for 7 passengers, while the Zodiac Cadet Fastroller 310 FR Acti-V INT-L 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 Mark II HD 2009 could be the deciding factor.
The Zodiac Cadet Fastroller 310 FR Acti-V INT-L 2008 has a documented top speed of 23 mph. Speed data wasn't available for the other model.
Bottom line: Choose the Zodiac Mark II HD 2009 if your priority is putting more people on the water — it handles 7 passengers and at 13,4 ft it has the deck room to back that rating up comfortably. The Zodiac Cadet Fastroller 310 FR Acti-V INT-L 2008 is the smarter pick if you want a lighter, easier-to-trailer boat rated for 4 that costs less to run day-to-day.