What are the advantages and disadvantages of using Bound Bow and Bound Dagger compare to ordinary Bow and Dagger?

They dont weigh anything, gives you more capacity for loot.

Bound Weapons don't weigh anything. They're pretty good for a couple of levels, but then they get "out matched" by the weapons you can forge yourself.

What is best looking inyo mind?

Bound Weapons only look like spectral Daedric weapons. You would likely see them for a long time.

I would personally use real weapons. You can continue to upgrade them so that they could do more damage. Not to mention you can always have a different bow and dagger.

Advantages:
Weightless.
Infinite arrows.
Soultrap/Banish with perks.

Disatvantages:
Lower damage.
Cannot enchant/upgrade.
Dissapear after a period of time.
Takes a while to cast/summon them.

Honestly, i only found them useful during the early level stages where my enchant/smithing/1-handed/archery ect were low, and stamina/carry-weight was low. Since they are Daedric weapons they do decent damage, but once you get the above skills up they become obsolete kinda fast and end up only being there for either roleplaying aspects, or aesthetics.

One thing with them though, they never stop looking cool but i wish they would have had ALL the weapon types... wtb a mace summon.