Selenium: PhantomJS is slower than Firefox

I wrote a Selenium test that clicks my ExtJS-Twisted web app and is very slow.

Can someone explain why PhantomJS is so much slower than Firefox in my configuration? What's wrong with urllib2 recv method?

Profiler statistics:

• PhantomJS

  Ran 1 test in 137.150s
  
  ncalls  tottime  percall  cumtime  percall filename:lineno(function)
  4485    124.000  0.028    124.000    0.028 {method 'recv' of '_socket.socket' objects}
  
        
  
          
          
          
        
  
      

• Firefox

  Ran 1 test in 36.660s
  
  ncalls  tottime  percall  cumtime  percall filename:lineno(function)
  96910   23.061   0.000    23.061     0.000 {method 'recv' of '_socket.socket' objects}
  
        
  
          
          
          
        
  
      

Network statistics:

[tester@server ~]$ tracepath 192.168.200.65
 1:  192.168.200.77 (192.168.200.77)                        0.207ms pmtu 1500
 1:  192.168.200.65 (192.168.200.65)                        0.773ms reached
 1:  192.168.200.65 (192.168.200.65)                        0.351ms reached
     Resume: pmtu 1500 hops 1 back 64 
[tester@server ~]$ tracepath 192.168.200.83
 1:  192.168.200.77 (192.168.200.77)                        0.087ms pmtu 1500
 1:  192.168.200.83 (192.168.200.83)                        0.733ms reached
 1:  192.168.200.83 (192.168.200.83)                        0.654ms reached
     Resume: pmtu 1500 hops 1 back 64

      

        
        
        
      

    

Testing machines:

• 77th web application works
• 65th run Docker
  
  since PhantomJS
  
  (reason: https://stackoverflow.com/questions/30618113/selenium-webdriver-socket-error-connection-reset-by-peer-for-non-root-users )
• 83rd launches local Firefox
  
  or PhantomJS
  
  65th against web app on 77th sec.