You probably already know the benefits of apt-get. Automatic update notifications, other apt-installed packages that need those tools know they’re installed, etc.
With pip, you know you’re getting the latest version at the time you install it, you can install to a non-default version of Python, and you can install to a virtualenv.
If you don’t need any of the features pip gives you, and you don’t routinely have to install other Python packages which aren’t available over APT, use the APT versions.