Bards tend to not be able to fight on the front lines using Martial Weapons. Although, being a Sword Bard might mitigate the weaponry concern.I think the Bard outperforms the paladin in almost every category except that nifty Aura. The bard is a much more flexible class that empowers many character concepts, and can even do a lot of what the paladin does by poaching their spells.
Seriously, a Bard can have find greater steed, banishing smite, or destructive wave several levels before a Paladin can.