Android Studio 3.0 and above require significant RAM (8GB minimum, 16GB recommended). For older machines running Windows 7, 32-bit systems, or low-power laptops, Android Studio 2.1.1 is lighter and more responsive.
For most developers, the latest stable Android Studio is the right choice. However, when the past calls, you now have the definitive guide to answer. android studio 2.1.1 download
Certain third-party libraries or proprietary SDKs were only certified for older IDEs. If you are stuck with a plugin that never received updates, staying on 2.1.1 might be necessary. Android Studio 3