Additional Pro:
Android Studio is ready for Android projects that use Gradle as their building system. Gradle is becoming the standard for building and testing your Android application. Check the Gradle Plugin User Guide in Android's website .
By the time of writing this answer, the ADT plugin for Eclipse does not support a Gradle layout style. Some hacking has to be done if you want to use Eclipse+Android+Gradle and an Android project with a Gradle directory layout what is quite inconvenient. See Integration of Eclipse with Gradle in an Android project.
