General

Pretty much everything relevant has been stated, so I'll just give my experience.

I didn't get my paladin past 138 because it just became boring. Then, when I switched back to my hero, I missed the massive defense immediately. I haven't played on it in a while, last time I did was before ACB became 2 hits.

@Retroreaper: I wouldn't say knowing which charges to use is unique or something.
Arch mages/evans can have the same issue with whether or not to use ele decrease; even then it's just common sense.
Once you know the right charge you just... use it. o_o
I find paladins more unique cause of their amazing defense and defensive skills.
Damage is something that can be achieved by funding, but no class can achieve a paladins defense/tankiness no matter how much funding they get.

OT: "Which one is cooler/more fun? I really don't care about damage unless its too weak to kill regular monsters."

No class is too weak to kill "regular monsters".
In my view Paladins are more fun, and cooler.
Heroes are much stronger after level 170+, though they are late bloomers because they have a lot of core skills to max.
Paladins are relatively weak without funding, but their defense makes bossing very leisurely; you can afk on zak/ht take a dump, come back, and you'll still be alive.
You'll also take literally no damage from monsters you train on (LHC) so you won't have to worry about HP pots.

"Paladins look cool because of their elements and cool 4th job skills. But I also heard they are boring?"

Really now? You heard they were boring?
It's not written in stone that paladins are boring, that's just peoples opinion.
Try it out for yourself and see if you think they're boring or not.
Paladins are hands down the funnest class I've ever played.

"Can anyone give me an input on the 2?"

Paladin = Defense.
Hero = Offense.