I was having problems with my internet speeds... I was having total buffering issues not only with Netflix but YouTube and a few other places... I always used DSLReports.com to test my speeds. AT&T sent me to speedtest.net... Suddenly my speeds doubled.
Somebody on a forum suggested that it was proven that speed test was given priority by various service providers to placate complaining customers by boosting the reported speed and blame shifting.
I haven't compared them in a while... Just a thought.