iOS 13 is better or ?

iPhone 6 is not capable of running iOS 13 or higher, so it's not a question of whether it's better or not. iPhone 6 hardware cannot support the newer iOS versions at all.

An iPhone 6 cannot update past iOS 12.5.4. It will never get iOS 13.

You can’t get iOS 13 for a 7 year old iPhone 6. The hardware is incapable of running anything newer than iOS 12.