Rogues are sneaky, and good at causing melee damage. They have one of the few real CC abilities, albeit it must be used before combat begins. They are definitely not off-tanks, but they can take a couple hits better than most other classes. Be a rogue if you like moving stealthily, or just doing a lot of damage with weapons.
Druids are casters that pretend to be hybrids. Their nuke damage is sub-par, but their healing is about up to snuff with a priest. They have the supposed best buff in the game, and the ability to change into a bear (and pose as a warrior), a cat (and pose as a rogue), or a cheetah or manatee to run/swim really fast. Be a druid if you want to cast spells but not be completely limited in your armor, if you're interested in healing but don't want to be a priest, or if you just like the idea of shape-shifting.
I have to agree with Jaefo though, the best thing to do is to try both to at least level 10...actually, a couple past 10 since that's when rogues get dual wield, but 10 is the apparent standard for being able to say you've tried a class.
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Only the exceptions can be exceptional.