Less of a pain in the ass for rapid iteration, zero overhead, fewer dependencies = less complexity.
Virtualenv is literally a set of shims in your $PATH and some tooling to manage those sets. Pyenv is the same thing, but extends the concept out to your actual Python interpreter and lets you rapidly switch between them.
Virtualenv is literally a set of shims in your $PATH and some tooling to manage those sets. Pyenv is the same thing, but extends the concept out to your actual Python interpreter and lets you rapidly switch between them.