Sooner Than Later vs Sooner Or Later
Although they look similar they have completely opposite meanings.
Sooner Than Later
(short for “sooner rather than later.”)
= something should be done quickly
Ex: You should tell her husband “sooner than later,” = You should tell him quickly.
Ex: You should see the doctor “sooner than later.” = You should see the doctor as soon as you can.
Sooner or Later
= eventually