When two boats share the same hull type — in this case both the Riviera Yachts 51 Enclosed Flybridge SII 2012 and the Riviera Yachts 5800 Sport Yacht - IPS 2013 are deep vee designs with fiberglass 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?

Size is the most obvious dividing line here. The Riviera Yachts 5800 Sport Yacht - IPS 2013 measures 63,0 feet overall (2013), giving it roughly 4,8 additional feet of deck space compared to the Riviera Yachts 51 Enclosed Flybridge SII 2012 at 58,2 feet (2012). Weight tells a clearer story for trailering families: the Riviera Yachts 5800 Sport Yacht - IPS 2013 tips the scales at 46 959 lbs — 42 153 lbs less than the Riviera Yachts 51 Enclosed Flybridge SII 2012 at 4 806 lbs. That difference is meaningful if you're working within a half-ton or three-quarter-ton truck's tow rating, especially once you factor in a motor, gear, and fuel.

The power gap is worth calling out. Rated to 715 hp, the Riviera Yachts 51 Enclosed Flybridge SII 2012 has a 280-hp advantage over the Riviera Yachts 5800 Sport Yacht - IPS 2013's 435-hp ceiling — enough to notice on acceleration and at cruising speed, particularly with a full passenger load. Fuel capacity breaks the other way: the Riviera Yachts 51 Enclosed Flybridge SII 2012 carries 978 gallons versus 7 gallons in the Riviera Yachts 5800 Sport Yacht - IPS 2013. On a lake day that's negligible, but for coastal cruising or long reservoir runs the extra range matters.

For family outings this is probably the sharpest distinction between the two. The Riviera Yachts 5800 Sport Yacht - IPS 2013 is rated for 19 passengers, while the Riviera Yachts 51 Enclosed Flybridge SII 2012 caps at 16. If you're regularly pulling extended family or a group of friends onto the water, the extra seats on the Riviera Yachts 5800 Sport Yacht - IPS 2013 could be the deciding factor.