The second example is legacy code inherited from C and written into early versions of Python, while the first was a late addition to version 2.7.x, i believe. It is far superior to the its predecessor in many ways.
This page compares the two…
Study the examples and in the end, ask yourself, which is more powerful and robust?
Aside
When the opening/closing quotes are single, we don’t need to escape double quotes in the string.
'The poem "{}" is written by {}.'.format(title, poet)