Ehhh!? I don't get this at all. You obviously do both.

1) you get your input data into the form that is meaningful in the database by validating, sanitising and transforming it. Because you know what form that data should be in, and that's the only form that belongs in your database. Data isn't just output, sometimes it is processed, queried, joined upon.

2) you correctly format/transform it for output formats. Now you know what the normalised form is in the database, you likely have a simpler job to transform it for output.

It's not just lazy to suggest there's a choice here, it's wrong.