Good question, I think it should be the corporate one, and even if it might be a bit more work to setup, it's definitely in the company's interest, since then the applications that are installed can be sandboxed and be vetted/whitelisted more easily.

App Store is disabled on my enterprise mac, same for my last job. I think it's fairly common.

Same as mine, but I didn't know if it was common or not.

On my company computer we can login to the App Store however we want. I created a new Apple ID with my work email but there would have been nothing stopping me from re-using an existing one.