They have the same function, but Google authenticator is tied to a specific device. Authy is tied to a phone number. To get the 2fa code from Google Authenticator, someone would need to physically steal your phone. For someone to steal the code from Authy they would just need to port your phone number to their phone, then they could just install Authy to gain access to your Authy account.
RE: Coinbase account hacked? Why two-factor authentication methods are not created equal.