No additional complexity was introduced into those two modules, aside from being a different language that's easily grasped by anyone who knows Python and C. LOC-wise, the modules were about the same as the Python versions.

I've done some integration of C code using ctypes, which works quite well, and offers the obvious speed boost, but feels less coherent and ultimately less maintainable, project-wise, than a well-coded Cython module. Writing a full-on CPython module from scratch would probably offer better performance than Cython if you know the quirks and are disciplined. But to someone who doesn't already drip CPython C modules, Cython is a godsend.

Ultimately, there's 5 commonly used ways (CPython, Boost::Python, SWIG, Cython, ctypes) to integrate C into Python, and right now you'd be crazy not to give Cython a shot, if that's your need. It's very easy to learn for anyone familiar with both C and Python.