When two boats share the same hull type — in this case both the Zodiac 550 2009 and the Zodiac Medline Sundream Zenith 2008 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 120 hp, the Zodiac 550 2009 has a 40-hp advantage over the Zodiac Medline Sundream Zenith 2008's 80-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 550 2009 is rated for 11 passengers, while the Zodiac Medline Sundream Zenith 2008 caps at 1. If you're regularly pulling extended family or a group of friends onto the water, the extra seats on the Zodiac 550 2009 could be the deciding factor.