Recs.
Updated
Specs
Pros
Pro You get in-game cards by buying real-world cards
Cards can be won and bought with won in-game currency but you don't buy currency with real-world money like other games. Instead when you buy cards in the real-world you get a code for the equivalent amount of cards in-game, theme decks give you the exact same cards, and promo boxes gets you those promo cards.
Pro Theme decks duels
You can play with pre-built decks against other pre-built decks. So if you don't have good enough cards for other modes, or you don't know yet how to make a balanced deck, it is a good way to get used to the game. And there are a lot of theme decks so you can play different games each time and try different game styles and strategies. At the same time, you know that the opponent's deck will not be much more powerful than yours. So victory depends mostly on you.
Pro Mixture between TCG and Digital CCG
The way the economy works and how it is possible to acquire the cards makes it a great niche between pure TCG (such magic) and traditional CCGs (Hearthstone). Cards have value, but its highly possible to grind and trade into it as a F2P player.
Cons
Con Mana screw/flood
Individual and often specific energy types must be attached to a pokemon before it can use its moves leading to situations with too much or too little energy.