It's not easy to differentiate a CI/CD service because integrations matter so much more than the service itself. Didn't even need to read any docs, it just works exactly as you expect it to.

Pros:

• Pipelines for running tests in parallel (freemium).
• Easiest setup of any CI service I've tried.
• Mandatory build status image service.

Cons:

• Test runners are alright, but not that powerful. Py.test can run tests in parallel on its own, but enabling that feature doesn't seem to speed up Codeship runs.
• Doesn't detect tox environments, so you have to specify one environment per pipeline manually.