Which one should I pick for a new project?

Based on the RepoPilot analysis, neither is ideal for a new project without careful consideration:

hugeterry/coordinatortablayout

The verdict is AVOID — Looks unmaintained — it's a solo project with stale commits. This is a significant risk signal for a new project. You'd be adopting a UI library with no active maintenance, meaning:

• Bug fixes are unlikely
• It may break with newer Android SDK versions
• No support for modern Android Jetpack components

reactivex/rxandroid

This is part of the larger ReactiveX ecosystem and appears more actively maintained than CoordinatorTabLayout, but the repository data doesn't include RepoPilot's full verdict for this repo, so I can't give you a definitive recommendation.

Decision framework:

• If you need TabLayout + CoordinatorLayout collapsing behavior: CoordinatorTabLayout is purpose-built for this, but you need to accept maintenance risk or be prepared to fork/patch it yourself. Check if modern alternatives like Google's Material Design libraries cover your use case first.
• If you need reactive programming on Android: RxAndroid is a proven choice in the reactive ecosystem, but verify its maintenance status independently beyond what's shown here.

For a new project, I'd recommend checking if Google's modern Material 3 / Jetpack Compose solutions already solve your UI problem before committing to either of these libraries.

FOLLOW_UPS:

• What specific Android UI behavior do you need to build?
• Are you open to using Jetpack Compose instead of XML layouts?
• What's your minimum target Android API level?