FastCGI cache vs W3TC

Hi …

This may be a simple question to many, but I’m still trying to figure out if I should use FastCGI cache or W3TC ? I have the following questions, which I hope the community can answer :

  1. When I install wordpress with W3TC option, then why does EE also install the Nginx Helper plugin ? Isn’t that plugin for FastCGI cache purging ?
  2. If installed with W3TC option, can I still ad FastCGI easily ? Will I have to do this manually ?
  3. I read that FastCGI is faster than a plugin. If so, why not just make FastCGI the standard option ?

Thanks, Lex