title: What are the primary differences between 'gc' and 'gccgo'?
body: <p>What are the primary differences between the two popular Go compilers, 'gc' and 'gccgo'?  Build performance? Run-time performance? Command line options?  Licensing?</p>
  
  <p>I'm not looking for opinions on which is best, just a basic overview of their differences, so I can decide which is best for my needs.</p>