Palia worths power up?!

I will personally power up one Palkia for the following reasons:
I like powering up diverse pokemon, especially legendaries.
Palkia is the second best dragon in the game.
Palkia has unique niches where it's better than Rayquaza.
I have the candy for it just from raiding.
I need it for pokedraft.
Palkia looks cool.

I would not spend rare candy on powering up a Palkia and I don't recommend it for most people. It's a good pokemon, but it's rarely that much better than its nonlegendary competition, and rare candy would be better spent on a Rayquaza.

If you already have a good selection of the strong Dragons (Dragonite, Rayquaza, etc.) then powering up too many Palkia's I think would be unnecessary. One seems enough in the current climate.

One because it looks cool .... as long you can field a squad of the better dragons

I got 100IV with lucky that make it easier for me to powering up for full

I want to power up one for variety's sake once it goes away. I have a low 30's Draco Meteor Dragonite rounding out my dragon squad that could use replacement.

Just see it as an improved version of salamence. I have a level 36.5 palkia right now, and I can confirm that it is strightly better than salamence. Not to mention it has more bulk than rayquaza, which I don't have a good one to max. However, if you have only enough rare candies to power up one legendary, I suggest to wait for dialga, because of higher bulk and max CP, but very slightly less DPS because of dragon breath and -5 attack.

Also excellent option for your 6 unique dragon team, if you have one.

I powered up two to Level 33 for Palkia rids and Latias raids, but I'd only got one evolved Salamence (hoping for Bagon day), and my two Rayquazzas have shockingly low IVs. It's cool looking and useful even if it's not the best dragon out there. Probably not the best investment, but if you like using it, it's far from a complete waste of candy/dust.