Celebi or Porygon-Z - which will be better in the meta? [SPOILER]
Here's my current conundrum. I hadn't read ahead on the Celebi quests and now have hit the task to evolve 2 'mon using items. I had enough Sunkern leftover from the last event that it was easy. But I'm not stocked up enough on candy for anything else right now, which means walking something like Scyther for a couple weeks to earn the dozens of necessary candy.
The exception being, I have more than enough for a Porygon2, but I was really trying to stock up that candy to prep for Gen4 and evolving a Porygon-Z.
So the question is - do I make the sacrifice of 50 Porygon candies in the short-term to get Celebi faster, or hold tight for the tier 3 Porygon? (Of note: I don't need to walk anything else right now for my 'dex - have just been stocking up on Gen4 candy.)
Answers
Given the odds that Porygon's evo-costs are likely to be reduced to 25 candy for Gen 4 I'd save it and find a nest for any of the other item evo mons. Oddish, Slowpoke, Poliwag, Onix, Horsea, Scyther, and Sunkern all nest. With Pinaps I don't see it taking too many catches to get the candy for them.
If Gen 4 gives it the moves that it doesn't have (Magical Leaf and Leaf Storm need to be in the game or it will pose problems for wormadam or leafeon) then celebi would be a nice future lockbox.
By the way, you can sacrifice the 50 porygon candies if you have lots of them, i had like 300+ or something and using 50 does not hurt much.
Leafeon's possible POGO movepool is currently Razor Leaf for fast and Leaf Blade, Solar Beam, Grass Knot and Seed Bomb for charge. It doesn't need any more moves to be added to the game since there's precedent of 1-fast move eeveelutions already.
EDIT: No idea why you mention Wormadam as a problem, it has at least half a dozen POGO quick and charge moves in its mainseries movepool.
As others have mentioned, Celebi won't be relevant in Go unless Niantic tosses it some new moves. As a Psychic-type, it gets outclassed in DPS by Mewtwo, Alakazam, Espeon, Exeggutor and company, and there are better options if you want a bulky Psychic-type such as Metagross and Lugia. As a Grass-type, it doesn't even register at the moment, as Celebi is unable to learn even a single grass move.