The best choice for passenger missions is the Federal Corvette. That ship can carry the most passengers. I even have one specialized for such missions. And yes, the biggest tank is the biggest bus. At some point they had specialized optional slots, like the military slots, but for passenger cabins. But after removing them the passenger liners were built to be combat ships. So since the biggest cabin uses class 6 slots they will not more such slots to those ships. They can be even bigger hull tanks then. So the Beluga is now basically just a niche ship with a big fuel tank. It don't have remarkable jump range and overheats very easily. It only advantage is to be the biggest ship, and carry most luxury cabins. But soon the "biggest" title is lost, and stacking luxury missions is not a big thing. So the Orca can do a much better job there. I own one, just to own one.
So the short answer is that the Beluga is not good at anything where it is supposed to shine. But if they brought back the specialized optional, added more of those and upgraded the FSD it could find its purpose again.
The Corsair vs the Python is what it is. Many ships will overlap and you can shape your fleet accordingly. I will use the Python, but that is because I have the ship kit with the extra lights. That fits the role I use them for very well. The T8 did also take a big bite of the Python territory, but that is progress. Soon the T9 will be more or less obsolete as well. They all end up as stepping stones towards the bigger ships.
