Even three years after Pokemon Go's release, a lot of trainers still don't know whether you should power up or evolve your Pokemon first.
Most trainers are familiar with what powering up your Pokemon does and, of course, anyone who has so much as heard of Pokemon knows the concept of evolution.
What is power up?
Firstly, before answering the question whether you should power up or evolve first, it is important to fully understand what powering up does.
Powering up your Pokemon essentially gets it closer to its maximum potential. There are 40 levels in Pokemon Go (for both trainer and the Pokemon themselves) and powering up gets you closer to that that maximum level.
When powering up you also need to account the diminishing returns of using precious stardust on increasing your Pokemon's power. As the level goes up, the more stardust it costs to increase it further for less reward.
It is worth noting that there is a big difference between CP and IV whereby CP is an aggregated statistic that combines a Pokemon's level and IVs.
So, now we know exactly what powering up does, we can discuss which to do first. Before the introduction of TMs, the Pokemon's moveset was more important. This meant it was better to evolve Pokemon first to find whether they had the desired move.
With that said though, there is no reason to waste TMs as they aren't a common resource. Therefore, the argument can be made it's more sensible to evolve first to see if you get the move you want for free.
In addition to this an evolved Pokemon will have superior base stats and consequently be better in battle.
It's a question that is continually asked within the Pokemon Go community but as the mechanics of the game stand, as discussed, there is little difference.
As with any other game, this could change however, so it would be wise to keep on top of any changes that are made.