When two boats share the same hull type — in this case both the Sea Ray 390 Sundancer 2010 and the Sea Ray 520 Sedan Bridge 2011 are semi displacement 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 Sea Ray 520 Sedan Bridge 2011 measures 52,3 feet overall (2011), giving it roughly 13,3 additional feet of deck space compared to the Sea Ray 390 Sundancer 2010 at 39,0 feet (2010). Weight tells a clearer story for trailering families: the Sea Ray 390 Sundancer 2010 tips the scales at 246 lbs — 204 lbs more than the Sea Ray 520 Sedan Bridge 2011 at 42 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 764 hp, the Sea Ray 520 Sedan Bridge 2011 has a 339-hp advantage over the Sea Ray 390 Sundancer 2010's 425-hp ceiling — enough to notice on acceleration and at cruising speed, particularly with a full passenger load. Fuel capacity breaks the other way: the Sea Ray 390 Sundancer 2010 carries 25 gallons versus 5 gallons in the Sea Ray 520 Sedan Bridge 2011. 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 Sea Ray 520 Sedan Bridge 2011 is rated for 15 passengers, while the Sea Ray 390 Sundancer 2010 caps at 11. If you're regularly pulling extended family or a group of friends onto the water, the extra seats on the Sea Ray 520 Sedan Bridge 2011 could be the deciding factor.