Originally Posted by nickdalzell
Siri can be beat on any device. Google Now is close, Sher.Pa is even better. then there is Alice, which imitates Siri and also uses Wolfram Alpha--the thing with Alice and Android, however, you can change the voice it uses, while Apple users are stuck with only one. i quite enjoy using a UK accent or Aussie accented voice.
Google Now is very nice. But, it is basically a voice-search engine. It doesn't really answer a question, but rather searches for it. For example, you can ask GN to set alarm clock, but you cannot ask it to cancel that alarm. You also cannot ask GN to turn on/off Bluetooth.
S-Voice (Samsung) can do all that. But, S-Voice is very limited in scope and takes longer to process...and does not always understand you.
Siri is ahead here of the two i mentioned...not by much though. I have not tried the others you mentioned.