The only difference between a Trader ID and a Smuggler ID is which side of the fence you support. Traders are more likely to fund lawfuls and Smugglers are more likely to fund unlawfuls.
That's about it ... they each can carry whatever cargo they like.
Honestly, I think traders should not be allowed to transport contrabands, and I'm not sure about them being allowed to land on unlawful bases. Well that depends on their tag I guess... any opinions?
As for a smuggler flying an Adv Train, I guess that is a bit OORP but it is more profitable than flying a Pirate Train. Unless I see a new Adv Pirate Train in 4.85 I think alot of smugglers will be using the Adv Train for now. Also, I don't think you want to fly a pirate train or transport into lawful space. They will definately stop just because it is a Pirate ship.
One more thing, do pirate trains have the same advantages and disadvantages of an Adv Train? Like how normal cruise disruptors won't stop them unless it hits the Adv train at the front area?