That pretty much sums it up. I've used both on different teams and like both. But everything in GitLab integrates so nicely that it doesn't make sense to break out of the box IMO. With the 2.0 API that just rolled out, CircleCI has flipped from "convention over configuration" to everything being explicit. I find that it takes a bit longer to write the config files in 2.0 but they're easier to read and understand what's going on because they're more explicit.
Since 2.0 just launched and they have solid example projects across languages, it's a good time to give it a shot. It'll be easier if you've never used the 1.0 version of the product IMO.
