This is the best card game out there.
1. Every update is significant and changes the meta, so that it never gets stale.
2. Unlike Hearthstone, you can easily understand how mostly every fighter and trick's appearance and name directly correlates to their abilities, like a Dogwalker with Hunt or how Lily of the Valley buffs elevated plants. This is attributed to PvZ's straightforward naming scheme (unlike WoW's naming scheme), and how George Fan, while making PvZ 1, wanted to make sure that the player could tell what any plant does purely by the design. This is another contributing reason to why PvZ was the perfect series to turn into a card game.
3. The lane-based combat system (in addition to the unique turn system) is a fresh take on the CCG battle system, which changes up gameplay enough so that the PVZH cards are almost never duplicates of cards from other CCGs, The lane-based system's restrictions arguably make for a more involving game than a pick-any-target system, since you can more accurately control what happens in the match, rather than letting your opponent decide what attacks what; Instead, the lanes decide what attacks what.
4. The dev team most likely wants to make every card viable without breaking the game or giving new players too good cards, so that they'll want to open packs to get better cards. They fix bad cards instead of letting them fall into obscurity, like with 90% of Hearthstone's cards.
5. This is the most rewarding CCG out there. Gems are easy to obtain, and legendaries appear 10% of the time rather than 5% of the time (like in Hearthstone).
6. Every single fighter has its own unique attacking, placement, destruction, and, sometimes, ability animations. There are hundreds of fighters in the game. Hundreds. All with at least 3 animations. Jeez.
7. Even though it may not look like it, the dev team does read feedback from the community, and, to prove it, one of them may edit the following statement: [Edited - Thanks for your feedback! - Admin.]
