Best Site To Check Connected Speed

What is the best site or way to check connect speed? I should have a 6mbps connection but it sure doesn't work like 6mbps. When I go to the speed test web sites I get speeds all over the place, some times it's around a mbps or less and sometimes it's 6 to 8 mbps. BUT, when I watch a video often it stops as it plays faster than it downloads, something you would not expect with 6mbps. Download are general around 250kbps to the upper 300's, again not what one would expect with a 6mbps connection. I understand it's not only my connection speed that determines the download speed but the other end as well but when I was getting good speeds (a couple a years ago with Comcast before all the jacked up prices and BS they all play with speed and bandwidth) I would often see download in the mbps range, NEVER see that anymore.