Many people new to GTD expect to find a tool to "do" GTD. Keep in mind that a tool doesn't do the thinking for you, it stores the thinking for you. So, then does it even matter which tools you use when it comes to organizing your projects and actions? Sure. Here are some questions to ask yourself when choosing what your GTD system will be:
Are there any tools already in place that you plan/need to still use? Like a corporate calendar?
Where is your email? Not required, but certainly helps to have your email and lists near each other.
Who else needs to see your data? Does it need to be on a shared server or would local be fine if you go digital?
What do you tend to be drawn to–paper or digital?
Is security a concern?
How would you back it up, if needed?
What are you willing to carry around?
What tools are you already familiar with?
Would you trust putting almost anything into it?
Is it scalable?
Can you easily learn how to use it?
What are you willing to pay for it?
What does it need to sync to?
Is there a perfect GTD system out there? Yes, it's the one you trust and use so your mind is free.