If you are looking for a testing platform for your android apps, your options are the AVD that comes with Android Studio, running android on a virtual machine or a standalone application like Genymotion.
While AVD is a very capable option, Genymotion offers some clear advantages, the main ones being speed and stability.
Its speed is closest to a real device, from boot time to app usage. Other unique features that Genymotion has are: simulate a GPS, use your computer's webcam as android cam and simulate battery levels.
You can select from many pre-configured android devices and choose on which android version you'd like to test your app.
I've never had any stability issues, which can happen with AVD at times.
Genymotion works on Windows, Mac and Linux. Its system requirements are modest, so any computer purchased in the last few years will run it comfortably. Installation is easy, however you must have Oracle's VirtualBox installed on your machine.
The user interface may not be as polished as Google's AVD, but it still looks nice, clear and easy to use.
The price for the personal version is reasonable (there is a more limited free version available).
The main "con" is that Google's Android Virtual Device Manager is available for free and is a very good option that does most of what Genymotion does.
Genymotion is not available on older versions of Windows (XP/Vista or any 32 bit Windows).
You have to create an account in order to use the free version. which is something I don't like.
There is no ARM support,no Android Wear support.
While Google's AVD always has the latest version of Android, Genymotion requires some time until it supports the latest versions.
If you are looking for the fastest nd most stable Android testing platform, Genymotion should be in your short list.
Testing and debugging on multiple android devices and versions with ease.