The hour is the occasion
A proposal or an anniversary is timed to golden hour, and golden hour moves month by month. A fixed departure cannot follow it.

Charters by day shape
The honest comparison between a private sunset dinner charter and a ticketed one — and when the ticket is genuinely the better answer.
A private charter buys the hour, the deck and the timing. A ticket buys a seat.
What you buy
Departure time
Guests aboard
Menu
Anchor position
Cost
Best for
If two of you simply want to see the sun go down over water, a ticketed cruise does that well and costs a fraction. Charter earns its price when the hour, the table or the privacy is the point.
When charter wins
The desk will talk you out of a charter if you do not need one. These are the cases where it does not.
A proposal or an anniversary is timed to golden hour, and golden hour moves month by month. A fixed departure cannot follow it.
A menu written for six people is a different thing from one service run for sixty. Dietary work happens before the day, not on it.
The captain sets the anchor so the sightline holds and nobody has to be repositioned. On a scheduled boat you photograph past other guests.
Send the date, the party size and what the evening is for. If a ticketed cruise would serve you better, the desk will say so.