Actually my point is with the Comcast plan, I do get consistent results regardless of the test sites/servers and the results are better than my new gigabit plan. Wth my new gigabit plan, I only get gigabit performance when testing with my ISP's hosted speed test server or a small percentage of servers hosted by other ISP (less than 10%). For the most part, regardless of the test sites (speedtest.net, testmy.net, speedof.me, speakeasy.net) I am getting sub 100Mbps speed when I should be getting gigabit speed.
And then there are some servers that would give me speeds in the 300Mbps for the download, but mid 900Mbps for the upload. These servers tends to be owned by other ISPs that have a predominant presence in my metropolitan area.
So this tells me the likelihood is that my ISP has poor peering. I am just hoping someone with a thorough understanding of how the Internet is interconnected can better explain what this poor peering actually means. Once I have a better understanding of why I am only getting gigabit performance up to the ISP's intranet and not on the Internet, I can file an intelligent complaint and help my ISP improve the Internet connections.