I use a T-9 for big haul tasks, mainly Operation Ida station repairs. Its fun to fly once you get used to the massiveness of the thing. However its the worst ship for evading interdictions and even struggles to evade NPC interdictions. Best to have another system locked in, submit to interdiction, drop heatsinks and chaff, and high wake the hell out of there. With this in mind, its best to avoid mission-type cargo runs as you will attract pirates. Don't even bother mounting guns, if you use them you've already lost.
The Imperial Cutter can at lease defend itself, but its crazy expensive and locked behind a rank grind.
Type-7 is a great trader. Smaller cargo capacity, but you will win every NPC interdiction and even some player interdictions. Similar to the T-9, no point packing guns really.
Type-10 is a good option if you like the big heavy handling and also want the ability to defend yourself.