The 90 is the one, and the reason is the fuel tank. Ten extra feet over the 80 buys you a 24-foot beam and 3,302 gallons against 2,113 — more than half again the tankage for a boat that is only 14% longer. On a line built around staying put and moving slowly, range is the spec that actually changes your itinerary, and this is the single biggest jump in the Ferretti catalogue for the length added.
The trade-off nobody tells you about is resale expectation, not fuel burn. INFYNITO is a young line answering a question the market has only recently started asking, and a 22-knot Ferretti is a narrower audience than a 31-knot one. If you are the sort of buyer who changes boats every three years, that matters. If you are buying the terrace because you have finally admitted you spend 90% of your time at anchor, it does not, and you will get more actual use out of this boat than out of anything else the yard makes.
One caution on the 80: take the optional MAN V12 1400s. Twenty knots on the standard V8s is enough until the one afternoon you need to get somewhere ahead of weather, and on a hull this heavy the two extra knots at cruise are worth more than the spec sheet makes them look.
— Tony Smith, Founder, Minted Yachts