Hello DutchKaos 😎
I think you are choosing between 2 very cool ships. They are both very different and i would say that the most common factor is that they both can carry cargo. You went with the military version of the Hercules so you get a perfect placed extra turret under the cockpit facing down towards the ground, so when you come in to land in a warzone to deploy troops and vehicles, that turret Will help clear a way for you. to me the fortress feel Will be helping out ground attacks and not so much in space. If you like a playstyle like that, transporting and supporting ground forces together with doing cargo runs the Hercules is for you.
On the other hand, if you want to be away in deep space for a Long time exploring the unknown and all what space is and its planets then go with the Carrack. You Will Also be able to do cargo runs in it aswell. The Carrack Also is a ship that has alot of extras like repair station, medical bay and so on. And remember you can Always earn the ship u dont get in game and/or help crew other people's ships that you like so you dont have to feel that youre missing out.
I have both ships but plan to play them differently.
If you just want to do cargo runs of that size ships i would go with a hull c and exchange some cargo with lots of turrets / defence platforms on it when they release that
Hope it makes you easier deciding