Suppose you are playing Dazzle and you sense a team fight is coming. You are ready to drop your ult, but the way everyone is positioned, you can either drop it on your friends OR your enemies. Which one should you choose and why?
(And, yes, I know it's better if you could do both. That's not the question here.)
Best Answer
There are way too many different situations to provide a definite answer.
I can give you a few pointers though: If your own team lacks a lot of inherent armor (physical damage reduction), and the opponent has a lot of physical damage (often a melee carry or a hard hitting ranged carry) then it might benefit you more throwing the Weave on your own team.
If the roles are reversed, and you can throw Weave on the enemy team and also be certain that your team can chase down the likely to be retreating team. Then that is obviously a great choice.
Similarly if the opposite team mostly dishes out magic damage, then Weave is almost in every situation better applied on the enemies as part of how much more damage your auto-attacks will do (even more so if this takes place early in the game where the armor values are quite low across the board).
I think the question might have to be a bit more specific to be properly answered though.