In terms of Tower Defense games, Radiant Defense does not disappoint. It looks pretty, the mechanics work, and you can set up the map however you want. But the issue is that it's just that. After a while, it will get kind of boring because it is the same kind of enemy level after level.
While there are benefits to playing this game, like it working with Android TV, it should serve mostly as a way to refresh the Tower Defense genre for you with the art direction and style. But since there is a paywall inside the game (you have to pay to unlock certain towers), this isn't something that would be played endlessly.
The game itself is a light download with a total game size of 17 mb. The economy supporting it is in-app purchases as the developers decided not to opt for ads, which seems like a nice touch -- until you reach the said paywall for more towers.
Anyways, number 6 might be a game you are familiar with, Castle Defense.