I would concur. Engines aside, the boat systems are identical, as are maintenance costs. One possible exception would be the inclusion of two heads on ex-charter cats. But then again, this feature provides for very happy admirals, so it's a
trade off.
You would be correct when it comes to
engine maintenance, but not necessarily
engine repairs, Both engines won't 'break' at the same time. In fact, engine redundancy is one of the benefits of
catamaran ownership. With twin engines...of course.