Responsive web : progressive or constant values between breakpoints ?

Hello,
According to you, is it better to use progressive or constant values between breakpoints.

For example :
font-size for an element :
before 767px (width of the portview) : 32 px.
after 767px : 68px.
the max width of the main container : 1300px

Would it be better to make the value of the font-size progressive from 32px to 68px depending on the width of container (from 767px to 1300) ? Or to keep it constant (68px).

Thank you.