I forgot to mention GitLab CI, but in my experience, much like with Travis CI, it is as you say lower level. I do not find that to be a good thing. Rather than

I forgot to mention GitLab CI, but in my experience, much like with Travis CI, it is as you say lower level. I do not find that to be a good thing. Rather than lower level being faster as it is with code, generally with CI we want to raise the abstraction level so that it's easier to make use of things that make CI run faster – parallelism in workflows, caching etc. As for reliability, I also found GitLab CI lacked the concurrency control caching primitives necessary to trust continuous delivery pipelines. I found you could either write a slow correct pipeline, or a faster but fundamentally unsafe one.