Hey Viola! They are mostly interchangeable, but "by contrast" tends to be more formal and direct in its comparison. 💡 If you need to practice English everyday, follow me and take the quizzes I share.

Yes. They have the same meaning and are used to differentiate between two things. What differs is how they are used in a sentence. E.g In contrast to yesterday's chilly weather, today is quite hot. Cats are very independent and aloof. By contrast, dogs are more affectionate and make great companions.