When two boats share the same hull type — in this case both the Zodiac 310 S 2009 and the Zodiac 690 2009 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?
The power gap is worth calling out. Rated to 250 hp, the Zodiac 690 2009 has a 235-hp advantage over the Zodiac 310 S 2009's 15-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 690 2009 is rated for 12 passengers, while the Zodiac 310 S 2009 caps at 4. If you're regularly pulling extended family or a group of friends onto the water, the extra seats on the Zodiac 690 2009 could be the deciding factor.
Bottom line: Choose the Zodiac 690 2009 if your priority is putting more people on the water — it handles 12 passengers and at 22,9 ft it has the deck room to back that rating up comfortably. The Zodiac 310 S 2009 is the smarter pick if you want a lighter, easier-to-trailer boat rated for 4 that costs less to run day-to-day.