I dont understand why there is a thread for comparisons like this.
Anyways TWEWY is more in-depth gameplay-wise and has a deeper gameplay, and on the other hand, Bastion is more immersive with it's great monologue voiceover and game atmosphere.
To me, TWEWY offers satisfaction that you get in games like Final Fantasy, while Bastion offers satisfaction similar to Diablo.
Both are great games, and choosing which one each player will choose over the other is based on what details they prefer more in a game.
By the way, Bastion is less of an RPG than TWEWY, but is more action-oriented combat-wise.