I've used both and recommend Poetry. It's got a larger feature set (it can be used to manage packages _and_ publish packages), it's faster, and it's more actively developed (measured by releases). Pipenv's last release was 2018-11-26, and Poetry has been publishing pre-releases as recently as three days ago to prepare for v1.0.0.

I did a quick comparison here[0], and I'm planning to do an update with the latest version of Poetry.

[0] https://johnfraney.ca/posts/2019/03/06/pipenv-poetry-benchma...