You could deal 2 types of damage, especially with enchantments. Even use one blade to give your enemy a specific elemental weakness, the other to inflict it.
Other than that and specific special moves, we have to assume it has been balanced to be a worthwhile trade off for speed or something.
This is the exact reasoning I used when deciding on my character type. See my sig.
Edit: to elaborate further, I plan on trying out the bleed effects with dual wielding axes combined with either more dots or other battle effects to increase the effectiveness of combating multiple targets at once. The Redguard racial is highly beneficial to this type of play. 10x stamina regeneration for 60 seconds will allow for a tremendous amount of dps--especially with enchanted/poisoned blades. It makes me excited even THINKING about it!