If you dual wield with a dagger in your left hand and a non-dagger (sword, mace, axe) in your right and you execute a sneak attack using your left handed weapon (the dagger) do you get the dagger bonus (x3, x6, or x15 depending on perks)? Or is the sneak attack bonus tied to your right handed weapon?

It is tied to the weapon. You cannot get a x15 bonus out of a sword. It needs to be a dagger.

I'm not trying to; I just want to make sure that I can get the x15 bonus out of the dagger even if it's in my left hand, and not my right.

You only get the 15x damage with a dagger in your right hand iirc. Most players tend to go with dual daggers if they are using sneak attacks.

You should receive the bonus and even see a little message pop up informing you of the sneak attack multiplier. So you could keep a sword in your main and a dagger in your left hand gaining the speed bonus in face to face combat and using the dagger to grant you the sneak attack multiplier. I'm not sure how the damage works when performing a dw sneak attack (sneaking up on an enemy and pressing both attack buttons at once). Hope that helps!

Edit - I used two daggers in my main playthrough and damage seemed to be the same regardless of which hand I used. (sometimes I wanted to use the drain life enchant in my off hand), of course this isn't necessarily conclusive of anything but I still saw the multiplier message regardless of the hand.

Hmmm....I think you only get the one 15x damage, which ever one hits first. The easiest way is to sneak attack with left hand and then try right to see if you get both.

I was actually thinking that I'd wield a sword in my right hand and a dagger in my left and that I'd rely on the dagger during sneak attacks if it can get full bonus, and use the sword when my target is too rude to die straight off.

If you are going for sneak attacks then carrying a sword carries a greater risk of being seen/heard than dual daggers. I don't know what the percentage is but it is worth considering in the early game when you need all the help you can get to stay hidden whilst moving in for the back-stab.

Keeping both on your quick list will make it easier to swap when you need them, you shouldn't need a sword if you have the assasin perk. The only time you need a sword is when you are out in the wilderness, daggers don't work to well against bears.

Actually... We were discussing this in another thread not long ago and I think you get both! So a dual wield Assassin's Blade strike would be 15(right weapon dmg) + 15(left weapon dmg). Assuming both are daggers.

Thanks for clearing this up, I only use the one dagger so wasn't sure.