The Larson LX 205 S I/O 2013 is a deep-V design and the Larson SEi 180 Ski Fish I/O 2008 is a modified-V design, so you're likely deciding between two noticeably different on-water experiences. Hull type shapes everything from ride quality and fuel burn to dock handling and resale trajectory.
Size is the most obvious dividing line here. The Larson LX 205 S I/O 2013 measures 21,1 feet overall (2013), giving it roughly 4,1 additional feet of deck space compared to the Larson SEi 180 Ski Fish I/O 2008 at 17,0 feet (2008). At 2 700 lbs and 2 650 lbs respectively, both sit in a similar weight class - either should pair comfortably with most mid-size SUVs and half-ton trucks, though always confirm your specific tow rating with the motor added.
The Larson SEi 180 Ski Fish I/O 2008 tops out at 225 hp. Engine specs for the Larson LX 205 S I/O 2013 aren't listed - confirm with a dealer before selecting an outboard.Fuel capacity breaks the other way: the Larson LX 205 S I/O 2013 carries 30 gallons versus 23 gallons in the Larson SEi 180 Ski Fish I/O 2008. 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 Larson LX 205 S I/O 2013 is rated for 8 passengers, while the Larson SEi 180 Ski Fish I/O 2008 caps at 6. If you're regularly pulling extended family or a group of friends onto the water, the extra seats on the Larson LX 205 S I/O 2013 could be the deciding factor.
Bottom line: Choose the Larson LX 205 S I/O 2013 if your priority is putting more people on the water - it handles 8 passengers and at 21,1 ft it has the deck room to back that rating up comfortably. The Larson SEi 180 Ski Fish I/O 2008 is the smarter pick if you want a lighter, easier-to-trailer boat rated for 6 that costs less to run day-to-day.