Does using virtualenvwrapper with Python3.3 mean I cannot (or should not) be using pyvenv?

Sorry this answer is a bit delayed. pyvenv does not aim to supersede virtualenv, in fact virtualenv in Python 3 depends on the standard library venv module.

The pyvenv command creates an absolutely minimal virtual environment into which other packages can be installed.

The Python 3 version of virtualenv actually subclasses the standard library's implementation and provides hooks to automatically install setuptools and pip into the environment which pyvenv doesn't do on it's own.

As far as I know virtualenvwrapper depends on virtualenv only because the mkvirtualenv or mkproject commands allow you to specify packages to be installed into the new environment, this only works because virtualenv will have already installed setuptools and pip.

So to answer your question I believe you should be able to use virtualenvwrapper on environments created by pyvenv as long as you follow virtualenvwrapper's conventions for where to put things and you either manually install setuptools and pip into the environment or don't use any package management features of virtualenvwrapper.