I believe that saying it's your one hour power is really just a shortcut. I think the ramp test is probably the most accurate for me. I did a couple of 8 minute tests, and I can suffer for that long if I want to make my ftp higher out of vanity. I think 20 minute tests are just too long for me, and I get discouraged. Getting a ftp that's too high is bad for systems like trainerroad, where they set the intensity based on your ftp. BTDT
I really should put a power meter on one of my outside bikes, I mostly have them to track training stress though.