I have a lugia 89iv with stats (15/15/10) is it worth powering up?
Whether your stats are A/D/S or S/A/D, those IVs are still pretty good, because Lugia is only lacking in attack, it's defence is insanely high and it's stamina is really good too, so one of them not being 15 is not as big of a deal.
Though power it up only if you actually need a Lugia, for example soloing Machamp raids.
Sky Attack is my favorite, as it claims effectiveness over most of Lugia's Psychic-vulnerable targets (such as Machamp), is very quick and safe to use, is two-bar, and maintains STAB against Psychic types.
Extrasensory is a high energy move that offers STAB, while Dragon Tail has incredible neutral coverage (only resisted by Steel and ineffective against Fairy), while also dealing good damage against Dragon Types, which (with the exception of the relatively-frail Gyarados) are vulnerable to the same type they wield. This means that Lugia doesn't take super effective damage but can also hold its own against Dragons.
I would use Extrasensory/Sky Attack for general purpose, but my current Lugia is Dragon Tail/Sky Attack to neutral other Psychic types (namely Focus Blast Mewtwo).
