I recommend https://concourse-ci.org/
- no hooks to manage worker scaling (https://github.com/concourse/concourse/issues/993). Our builds are _heavy_ and we'd run up an enormous AWS bill without something like (https://wiki.jenkins.io/display/JENKINS/Amazon+EC2+Plugin)
- no way to restart a build, resorting to 'empty commits', which is a huge red flag for useability (https://github.com/concourse/concourse/issues/413)
- limited documentation/examples (network effect)
Concourse definitely feels more refined than Jenkins. Like other commenters have said, it's a steep learning curve to grasp how things move between Tasks/Jobs.