Which is better for testing, Appium or UIAutomator?

After research for testing Android app code, Internet gave some testing tools options as follows:
Appium (Android & iOS)
UIAutomator (Android multi app interaction)
Espresso (Android single app interaction)
Robotium (Seems old now)
Calabash (Command line)

Among all these Appium and UIAutomator were picked up.

So which is better among these two?