Also let me know on your opinions on what advanced class to take

So I've been gone from Swtor for a few months and I'm starting back up again. I want to give a new class a try but I'm not sure what to play. I have a Scroundrel and a Merc. I want to play a Melee class but not opposed to ranged just want to know which story line is the best throughout the classes I have not played. Any opinion would be greatly appreciated