The Marathon Otisco 12 2010 is a flat-bottom design and the Marathon Seneca Utility 12 2009 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.
On paper these two are close siblings in the size department - Marathon Otisco 12 2010 at 12,0 ft versus Marathon Seneca Utility 12 2009 at 11,0 ft. At 110 lbs and 121 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.
Both boats share a closely matched power ceiling - 7 hp for the Marathon Otisco 12 2010 and 10 hp for the Marathon Seneca Utility 12 2009. Real-world performance will come down more to which motor is actually bolted on, its load at the time, and whether it's a 4-stroke or 2-stroke setup.
Both boats are rated for 3 passengers - a good fit for a family of four or five plus guests. Comfort at capacity is another matter; the longer hull typically means more seat options and better weight distribution.
At this size, power-to-weight ratio matters more than outright horsepower. The Marathon Seneca Utility 12 2009 comes in at 12 lbs per hp versus 16 lbs per hp for the Marathon Otisco 12 2010. The lower the ratio the more explosive the acceleration - meaningful on a short RIB where bursts of speed, quick planing, and agility in surf or tight waterways define the experience.
Bottom line: The Marathon Otisco 12 2010 and Marathon Seneca Utility 12 2009 are closely matched on the specs that matter most. Test-ride both on the water you actually use, check current dealer pricing, and factor in long-term service access before you sign.