Seafarers Or Cities And Knights Settlers Of Catan Cities & Knights Or Traders & Barbarians?

Settlers of Catan Cities & Knights or Traders & Barbarians? - seafarers or cities and knights

Catan I've been playing for about a year and I am looking for a little more complexity and depth. I was told that the sailors did not add much to the size of the game, and I found many reviews of T & B, particularly in relation to C & K. What does this suggest to anyone? Is it true that made T & BC & K really needed? Thank you.