[Joe Staff]

Well technically speaking, files are the fastest method. But the difference between saving an account's information via SQLite or files is literally within 1 or 2 milliseconds, not noticeable to anyone. However; SQLite is far more organized, you can keep all information including bans, accounts, and server information in a single organized-file. So in the event you need to change servers or create backups, it will be no different than downloading and uploading a file probably no more than 10MB in size.

For a valid example of SQLite account system, take a look at my Assassin's Escape gamemode I publicly released a long time ago.