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When it comes to consistent damage output, a barb or fighter overshadows a Paladin. When it comes to situational damage output, a Paladin can rack up some pretty good damage.
Also, if your DM doesn't throw out magic weapons like candy, then there is a good chance that Bless Weapon will be quite useful against creatures with very tough DR.
I would also argue that the Paladin bonus saves, immunity to disease and fear, detect evil, and lay on hands is often more useful during an adventure than barbarian rage or fighter bonus feats.
Throw in all the extra spells, feats, and the uber mounts from Defenders of the Faith, and the Paladin is quite on par with any other class in my opinion. Personally, the paladin I am playing right now doesn't do as much damage as our fighter, but he sure stands up to spell effects and such much better. I don't know how many times the fighter has been held by a hold person spell, confused or feared while I just keep on fighting.
Paladin class is very strong, easily on par with the other melees for overall class abilities. I would go so far as to say better than the other melees when enhanced with spells, feats and mount from Defenders of the Faith.