[penguin3107]

The two are similar in a sense that they accept voice input.
However, they are very different in the way they operate.

Vlingo will accept specific voice commands.

Siri is contextual, and will accept anything you say to it and it will interpret the request on its own. It understands intent, which makes it far more advanced than Vlingo. Basically, You can speak to it naturally, rather than sounding like a robot.