Which legendary bird power-up?

Good luck being patient waiting for Mamoswine. One year wait at least. Is to be seen that it outclass Articuno, though.

Zapdos is a must, in my opinion. I wouldn't power up lugia unless you really need it to solo machamp

Its so stupid to wait for gen4 and raikun. These are gonna be best pokemons of their types for a long while.
i think lugia is better then mewtwo to use with psychic moves

Entei will be way superior to Moltres. Zapdos and Raikou are about equal statwise if you argue this way...Mewto will be better than Lugia for sure but to get Mewto Lugia could gain you a lot of extra balls to even get a Mewto. For me it depends really on what you already have..

I have 4 Flareon and an Arcanine powered up, so Moltres somehow doesn't make a lot of sense for me even though I habe one at 96%. I also have a Lapras and a Cloyster powered and since Ice really won't be needed until Dragonite becomes a raid boss, Articuno is not useful at the moment. Zapdos is probably the best of the three but electric isn't as good as it was when gyms were flooded by Gyarados. Since I have a Jolteon and a Magneton I'm not in a hurry here even though I have one at 91%. That's why I went with Lugia. 93% DT/SA at 3150! Mewto won't like her^^