If I were to choose one for a new player, I'd personally say start with Paladin. It's easy to learn, has a very versatile kit, and its utility is extremely valuable in many situations.

If I were to choose one based off of preference to someone wanting my personal preference of tank, I'd choose War. Despite its less versatile kit its a a joy to pick up and go blast some boss to pieces with 5 fell cleaves, an upheaval, and an Onslaught while being able to tank huge hits with the ever joyous Vengance. (and I can't think of a group I've been in that doesn't have one, personally.)

If I were to choose one based off of what would challenge someone the most, I'd choose Dark Knight. It's less versatile kit requires you to think outside of the box at times and practice a harder to optimize rotation, but once you get the hang of it is a blast to play just as the other two, and is even amazing against certain bosses with how its cooldowns align or how it has Dark Mind making it a king against magic damage bosses.


But if you want aesthetic, can't argue with the simplicity of a sword and board or a guy with a giant sword.