The right answer is not a preference. It falls out of your route length, your ticket price and your load factor.
Operators usually arrive having already decided, and often on the wrong side of the maths.
The question is simple: what does an hour of passenger comfort earn you on this route? On an overnight run of nine hours or more, a berth commands a fare premium that pays back the lost seat count. Under about six hours it rarely does, and a semi-sleeper with a higher seat count wins on every load factor you are likely to see.
Bring your route length, your current fare and your average occupancy. The layout usually picks itself.