I just tried Google PageSpeed Analysis in the developer tools, Google Analytics and the website itself (https://developers.google.com/speed/pagespeed/insights). Now, in each of them I get differing results (sometimes with a difference of 30 points!), which makes it seem unreliable. The FAQs discuss the difference to Webmaster Tools, but in particular the developer tools and website should give me the same results it says.
Why the difference?