As you can infer from the name, pybin11_catkin is a:
Catkin wrapper for pybind11
which basically means:
This repository wraps the recent releases of pybind11 for use in catkin-based projects.
Among other things, this makes it easy/ier to build / use pybind11
in Catkin (and Colcon) workspaces, and consequently, ROS packages.
Other advantages would be the use of this package across different OS (which may not have pybind11
, but do support Catkin workspaces/ROS) and a more homogeneous development environment (pybind11
available at the same version everywhere).
See ipab-slmc/pybind11_catkin#3 for what appears to be a discussion around utility of the package. This links to arturmiller/pybind11_examples for some examples.
I would rather use the one from Ubuntu
By all means do.
If you are on an OS which packages pybind11
at a suitable version and you don't need/want to depend on the Catkin wrapped version, then don't use it.