Now with all the basic stealth perks, daggers will do 15x damage, while one handed weapons do 6x damage. However, one handed weapons have the One-Handed Prowess perk that, as far as I can gather, makes one handed weapons except daggers do 20% more damage per rank, with 5 ranks in total. That means double damage at rank five, translating to 12x sneak attack damage. Now, this is still slightly less, but with other one handed weapons having higher base damage compared to daggers (something that seems probable), this difference quickly disappears. This is also not counting the extra perks for armour penetration, critical damage and bleeding from maces, swords and axes respectively.
Now, don't get me wrong. Daggers are still useful in that they can get the same amount of sneak attack damage in fewer perks (though the 15x one requires 100 sneak), but if one considers fighting toe to toe using melee weapons at least some of the time, one handed weapons other than daggers now seem superior in my opinion.
There may be many reasons why I am wrong on this, though. The one-handed-prowess perk might not work on sneak attacks, for instance. For information about perks I have used the Elder Scrolls Wiki (http://elderscrolls.wikia.com/wiki/Perks), and the information here might not be accurate.
Have I misunderstood something here, or does all this seem correct? If so, what do you think of it? If you were planning on having your character use a dagger, have you now changed your opinion?