I think every class has their ups and down if we're going to look at this from a role playing viewpoint.
Paladins for example, fancy shiny armor, being able to shatter every rib of your enemys chest with your hammer, and at the same time heal any wound. But you are also likely going to be some religious fanatic, who goes on every day about serving the light to the point that it will consume your life.
Same with druid, sure it would be cool to shapeshift and prowl around in the world, but you're also going to be this nature crazed freak who gos around to smell every flower to make sure they doing well, bringing medicine for the sick animals and sit and sing for the trees all day ...
Warriors, sure you would look ferocious in battles and probably win every pub brawl, but you will definitely just have a general anger problem in your every day life.
Warlocks will probably not have a pretty life as your entire existence will be based on playing around with your own soul and others, doing crazy evil rituals and playing with death. You will defiantly be the outcast of society with your only company being some demonspawn you've summoned from the depths of hell.
Druid, without a doubt.
1. You can fly. (Can anything top that?)
2. You can be invisible and go/do whatever you want on the ground.
3. You can swim as much as you want without holding a breath.
4. You're arguably the fastest moving creature on any "platform".
5. You can heal yourself in case anything has happened to you.
6. You can resurrect your friends.
7. And if "played" well, feral can shred you to pieces as well. :D
Same with druid, sure it would be cool to shapeshift and prowl around in the world, but you're also going to be this nature crazed freak who gos around to smell every flower to make sure they doing well, bringing medicine for the sick animals and sit and sing for the trees all day ...