APPIUM Advantages:
Open source (free)
Cross-platform
Supports automation of hybrids, native and webapps
Supports any programming languages.
Support for various frameworks.
Doesn't require an APK for use,although automating certain apps do.
Backend is Selenium so u will get all selenium functionality.Selenium webdriver compatible.
Supports any programming languages.
Commonly used programming API's can be integrated.
Can run app through appium server without manipulating the app.
CI compatible with jenkins, saucelabs(so far from my experience)
Able to run on selenium grid.
Doesn't require access to your source code or library. You are testing with which you will
actually ship.
APPIUM Disadvantage:
Doesn't support image comparison.
Limited support for Android < 4.1
Under Developing stage can't use for big project initially
Appium documentation is a little weak
Less availability of tutorial