When two boats share the same hull type — in this case both the Zodiac IV 2009 and the Zodiac Pro 850 2011 are inflatable 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 350 hp, the Zodiac IV 2009 has a 50-hp advantage over the Zodiac Pro 850 2011's 300-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 IV 2009 is rated for 15 passengers, while the Zodiac Pro 850 2011 caps at 10. If you're regularly pulling extended family or a group of friends onto the water, the extra seats on the Zodiac IV 2009 could be the deciding factor.