Daggers are terrible for everything except sneak attacks. They have no 1h perks for them and they don't benefit from +1h dmg enchants on your armor.
If you are backstabbing, daggers are good (but pathetically not as good as maces if you have a full set of enchanted gear). Anything else daggers are terrible.
What a perfectly terrible answer... first, you're wrong - 1-handed perks DO affect daggers and dramatically increase their DPS (through Armsman), it's only the +damage gear/enchants and weapon-specific perks that don't. This may be a bug. Second, my dual daggers make absolute mincemeat out of enemies, and are far more appropriate for my sneaky, assassin character. Plus, backstabbing my way through a fortress is damn fun.
Your answer looks like copypasta from an MMO forum... the truth is both are equally viable, and how much enjoyment you get out of either will depend on your playstyle/preferences. Since both raise the 1-handed skill, you can freely switch between both if you prefer, or try your shiny new dagger for a few levels and then switch back to dual swords without any detriment to character development.
If you're seeking pure damage, non-daggers are certainly the way to go at the moment, but the difference doesn't really matter since you're insta-gibbing everything regardless from sneak...
-P