Each of the four callings (Warrior, Cleric, Rogue and Mage) has its strong and weak aspects, so it is not about which one brings you the best advantage, but rather which one suits your interests and personality best. Which of the four callings did you choose for your character?
I took the Rogue! I love the ranger style ranged character, bards, and weird utility classes like the Tactician. The rogue had all these as souls, a few more damage dealers, and my favourite type of tank, a cooldown based/reactive tank. It was definitely the calling for me! It does suck a bit in PvP, where we're the weakest class overall. I just have to try and play around my weaknesses, though.
I opted for a mage my first time through the game at release, but quit at level 22. Upon returning a few months ago, I went with cleric. People call them the OP class, but you can't beat their versatility. If you want to heal, you have 3 (now 4) different styles of healing. Want to tank? You can do that, too! If you love doing dps, there are options there as well. Caster? AoE? Single target melee? AoE melee? I don't regret my decision one bit. Having said that, the only other class I have at max level is a rogue. While I LOVE the assassin role, there's no application for it in PvE. You can't interrupt, you can't AoE. I think with her I just need to find the perfect role before I really enjoy her.
I went Pyro Mage. Absolutely tears things up! I one shot most mobs and can solo most elites. Don't even get me started on PvP. Being level 21 and killing 29s like it was nothing. XD
Rogue for me as well, I just love the fast paced combat. Come to think of it, I`m playing Rogue on almost all MMO`s that I play.
I picked mage for my first character, I intended to go healer but instead I have a lot more fun spreading dots on everything
Warrior, I like the straight forward play style of the warrior, I 'm more of a brutish gamer than a tactition
Cleric was my choice. I am aiming towards a mix between DPS and healing so I can be useful in a team while doing raids, rifts and such. I still haven't chosen what my main role would be, but I am sure I will find it. However, I find that all 4 callings are great and balanced.