How normal is it to say "on the contrary"?
Example:

Person A: It is much better to buy cans of soda than bottles because you can store them more easily.

Person B: On the contrary, I think bottles are better because you cannot seal cans once you open them.

Question

How normal is it to say "on the contrary"?
Example:

Person A: It is much better to buy cans of soda than bottles because you can store them more easily.

Person B: On the contrary, I think bottles are better because you cannot seal cans once you open them.

Answer

Perfectly normal. It is a  relatively formal but often heard.

Answer

Yes. it's perfectly normal to say. Sometimes we borrow the French expression, "au contraire", so don't be surprised if you see it in an English text.

Answer

If someone used the expression "on the contrary," I would think they were being a bit stuffy and pretentious. Like in an academic discussion. It doesn't sound natural in everyday conversation.