for performance oriented tasks, you may use Genymotion and if you are looking for the Lollipop emulator then go for AmiDuOS.
You can also use the standalone Android OS (ISO morphed into bootable device) which is not dependent on your host and helps leveraging true performance of the installed HW.
If you're completely new to this kind of emulation then Andy is the way to go. Its free and robust without any caveats.