Do you usually purchase digital or physical books? Why?

Physical only.

There is no way that anyone can take the book from my shelf. OK technically they could break in an steal it. But they could not remotely disable it. Or remotely delete it. Or the ebook for some reason is no longer in an electronic format that is usable. The government couldn't ban it and force it to be remotely removed.

I own it. The world can take a flying leap off a very tall building.