leaderboard data - xml, database or PlayerPrefs

Hello everyone, I want to create a leaderboard for my game and I got confused by what I found. I saw people using a database, some use xml, other used to store through PlayerPrefs.

What is the different of these three ways? I think PlayerPrefs is used locally? the other two to be published online later? am I correct?

In my case, there is chance for my game to published online. So, what do you think is better xml or database? I totally prefer working with xml, but in situation like leaderboard is the database better?

Thank you.