For image size, it doesn't matter. It does matter for build time.

Specifically, multi-stage builds let you get better caching and therefore faster rebuilds, since you can cache the pre-installed gcc etc. layer, while still getting the small image.

So if you have a human being waiting on frequent Docker build results, yes, multi-stage is better.

In this case, the builds are automated, no one waits for them, so it doesn't really matter (except for burning some extra CPU cycles).