Power up Moltres?

I think it is the best fire type. But what does that mean really? Do we have a big need for great fire type mons?

It's the best fire attacker and it's also in the top 5 for neutral dps.

I will power up my 93 % one, knowing that eventually Entei will come, which is better. In a super effective matchup, they are very close, in a neutral matchup Entei will have better survivability.

For now, it is the best fire attacker.

If you had over 300+ rare candies, I'd power up one of each legendary to Level 30...eventually...I think it's wise to save 200+ to max a Mewtwo and after that, take other stuff to Level 30 for fun (if high IV).

I only have 1 Legendary over 90% so that's on my plan eventually...

I'm powering up my best of each legendary to at least L30. Unfortunately that means powering up a few with very middling IV's as I have had terrible IV luck with legendaries. I have seen a handful of 95%+ IV ones, but never caught one. The best of my 25 caught legendaries is a 91% Zapdos. My best Articuno out of 7 is a measly 82%.

Anyway, in turns of "worth" I think current legendaries goes as follows in the CURRENT META (which is always subject to change):

1) Zapdos (clearly the best current electric mon)

2) Moltres (best current fire mon, but you probably already have several Flareon, Arcanine and Charizard, so the added value isn't necessarily that amazing)

3) Lugia (A pretty good tank)

4) Articuno (mostly just a Dragonite counter and it even gets wrecked by Steel Wing. Might be useful against future dragons, but you could wait until then if you are low on dust).

I powered my best one (93%) up to 30 already. I've also powered up a Zapdos (91%) to 30. Of course, I now run a risk of catching a better one of each in the next week or so. But that'll be the price I pay for my impatience. I caught a 93% Zap yesterday, but that's not a big enough difference for me to get upset over. (And yes, I'm aware of the irony of being afraid of catching a high IV legendary.)

As others have said, I plan on taking at least one each of all legendaries to 30. Lugia will be next (as soon as the event ends). Articuno can wait a while, but it'll also get there.

Moltres has an extra resistance against grass and a resistance as a neutral attacker against fighting, but loses the fire resistance to ice.