When threads_a_gogo beats node 2 to 1.... or does it?

bench.js

/*

$ node bench.js 
Threads_a_gogo JS thread ->  3039 (ms)  298607040
Node's main JS thread    ->  4677 (ms)  298607040
Ratio: 1.54 times faster than main JS thread
New, separate VM ->  3065 (ms)  298607040
Ratio: 1.01 times faster than new VM

*/


var vm = require('vm');

function fib (n) {
  return (n < 2) ? 1 : fib(n-2)+ fib(n-1);
}

function loop (n) {
  var r= 0;
  while (n--) r+= fib(35);
  return r;
}

function cb (err, data) {
  var save_t= t= Date.now()- t;
  console.log("Threads_a_gogo JS thread -> ", t, '(ms) ', data);
  thread.destroy();
  
  t= Date.now();
  data= loop(20);
  t= Date.now()- t;
  console.log("Node's main JS thread    -> ", t, '(ms) ', data);
  
  console.log('Ratio: '+ (t/save_t).toFixed(2)+ ' times faster than main JS thread');

  t = Date.now();
  this.loop = loop;
  data = vm.runInNewContext("function fib (n) { return (n < 2) ? 1 : fib(n-2)+ fib(n-1); } function loop (n) { var r= 0; while (n--) r+= fib(35); return r; } loop(20)", 'looper');
  t = Date.now() - t;
  console.log("New, separate VM -> ", t, '(ms) ', data);

  console.log('Ratio: '+ (t/save_t).toFixed(2)+ ' times faster than new VM');
}

var thread= require('threads_a_gogo').create().eval(fib).eval(loop);
var t= Date.now();
thread.eval('loop(20)', cb);