Lugia v Mewtwo
Just thinking about which quick move I want for Lugia. I think I'm going to have it in my Mewtwo squad as a tanky option to keep me in the fight. Dragon Tail seems far superior to me, but this site suggests Extrasensory is equally viable. But doesn't DT have superior true" DPS plus neutral (unresisted) damage into Mewtwo? Sure I'm missing something, but what? :-)
From my understanding, it's Lugia's charge move, specifically Sky Attack, you'll be using the most often. As he takes damage from Mewtwo, he'll be increasing his charge bar allowing you to use it almost constantly.
The quick move therefore doesn't really matter. Extrasensory has better EPS to assist with the initial charge, but Dragon Tail will do more damage. Overall, for fighting Mewtwo, I'd say they are more or less on par with each other.
I agree with the others that Extrasensory would be better. The theoretical kill speed advantage of dragon tail over extrasensory in a Mew2 raid is about 4%. On the other hand, an extrasensory/sa lugia doubles as an excellent attacker in Machamp raids. At least for me that makes more than up for the missing 4%.