This is just my own testimony, but there are numerous features in tweet bot which Twitters own app doesn't even attempt to provide. Such as conversation threading in both directions (twitter only let's you see In Reply To). The app is also quite a bit more polished and better behaved (Twitter Mac triggers my discrete gpu, Tweetbot doesn't). Twitter Mac doesn't even support gestures.
As for the website... Twitter loses all its value to me if I have to open a browser every time I want to read content.
As for the website... Twitter loses all its value to me if I have to open a browser every time I want to read content.