While Siri is great for hands-free commands on your phone, a recent experiment by Apple Analyst Gene Munster proved Google to be a bigger winner in the 'search' department than the iPhone voice command.
Siri can search your contacts, find movie showtimes, and search for stuff online for you. But the chances of Siri mucking up your search results run high. For example if you ask Siri when a movie was released, it'll give you a movie theater search instead. Or it could misread your pronunciation and suggest other things.
Typing into Google proved much more efficient and straight to what you're looking for. So if you have able fingers, use Google instead.
However that doesn't mean you should cut Siri out of your life forever. Instead, find out what Siri does best for you - like text messaging or calling a contact whose name it understands.