I use Google Cloud Build because it's my first foray into the CICD world(loving it so far), and I wanted to work with something GCP native to avoid giving permissions to other SaaS tools like CircleCI and Travis CI.
I really like it because it's free for the first 120 minutes, and it's one of the few CICD tools that enterprises are open to using since it's contained within GCP.
One of the unique things is that it has the Kaniko cache, which speeds up builds by creating intermediate layers within the docker image vs. pushing the full thing from the start. Helpful when you're installing just a few additional dependencies.
Feel free to checkout an example: Cloudbuild Example