f-string is easier to read, write, and less computationally expensive than legacy string formatting.

f-strings provide a way to embed expressions inside string literals using minimal syntax. Through this f-strings are readable, more concise, and less prone to error than other ways of formatting.

Legacy string formatting such as printf style and .format(...) are less readable than f-strings. Given that these are completely equivalent:

value = f'{user.first_name} {user.last_name}'

value = "%s %s" % (user.first_name, user.last_name)

value = '{first_name} {last_name}'.format(
    first_name=user.first_name,
    last_name=user.last_name
)

Why not choose the easiest to read, write, and quickest to execute (the first one)?