[Xurinos]

I can't speak for the other two systems compared, but to be clear, OP's examples involve more than "dictation and simple searches"; Siri also controls the device. Without entering the text messaging or email apps, one can tell the virtual secretary to read and write messages and emails. Assuming Siri understands your voice well enough.

Fun specific example at the lock screen after holding down the iPhone's button for a couple seconds: "Read the latest message from my wife to me." Then, still at the lock screen, "Reply to my wife I love you".

Maybe it's just my experience, but I did not care much for Siri until she allowed me greater control over my device. When she first came out, you could not ask her to read the screen; later, the program was able to toggle assisting configuration like VoiceOver by command.

[escapologybb]

^This

Siri was essentially a curiosity for me until they allowed me greater control over the device, but I use my iPhone in exactly the way you've just described.

Along with "am I meeting with my physiotherapist today?", and "arrange an appointment with my doctor, physiotherapist and partner" at which point Siri creates the appointment in the calendar and sends an email invite to the parties mentioned. Assuming those people are in your contacts obviously.

[jonknee]

Sending email and text messages have been part of Siri since it was bundled with iOS...