It is very clear, but you don’t seem to want to understand that the design doesn’t make much difference - the O class ships may have the most open deck space but that doesn’t mean it’s the one you’re going to find the most open space on which to relax. And, the answer is so variable depending on sailing, itinerary, capacity that any answer would be meaningless.
On paper you could find ship x has exactly what you want, you book it and then when on the sailing you find out that your particular sailing is a partial charter where a section of the deck is off limits (or over run by kids, or chair hogs, or at 120% capacity, rains all week etc) which throws off your whole plan.