Lugia: Shiny or IVs?

IVs.

A shiny with poor IVs is just a trophy defender. And shiny legendaries can't be defenders, so they are only trophies for 30s of a group raid fight or trophies for screen caps on social media. Neither of those require you to actually power up the stupid thing.

Lugia is a trophy more than anything. It has some uses here and there but ultimately nothing that will come down to a 15% difference in IVs.
So shiny for me.

Hold on to your dust for other pokemons. I would not spend any dust on powering up lugia atm. Sure it can be used in machamp solo raids but 6 dragonites can easily do the same job even if its a weather boosted machamp (have tried it successfully). In the end, its just my opinion so feel free to do what you feel is best for you. Cheers.

For me, 100% Lugia > any shiny less than 90 iv.
A 15attack 82+ IV shiny > any lugia non 100%
Ps: i personally wont maxed out any legendary wo 15A.
Hope you get a better one before it leaves. For now, 93iv one will be my choice^^