The Android 4.4 Kitcat has integrated ‘ART Compiler” into the operating system. From the developer option screen, You can select to use Dalvik or ART as the runtime compiler for running applications.
Android is a system that uses the Dalvik virtual machine to manage and run applications. The New runtime compiler, ART, the technology developed by Flexycore, allows you to run Android applications in a much more quick, fast and direct way as if Apps were native and not moved through a virtual machine.
It is important to keep in mind that this is currently “hidden,” as it breaks the emulator.
By the way, some one has post a ART vs Dalvik bentchmark test. Here you are: