bios default mode

Can someone explain what the difference is between ASUS Default(F5) in EZ Mode vs Load Optimized Defaults in Advanced Mode (F7) under Exit tab? If you were going to do a BIOS update what would you choose to reset to factory settings for a clean BIOS update? Are they the same?

Hi guys, can you please help me? After time to time my bios set up into default mode, after starting PC or after restarting windows? Any help? Why? I have i7 6700K with MB Z270-Ultra Gaming, i have OC on 4,6Ghz/1,38V. L.