i've found that they are pretty darn close tbh. the hour test is terrible, but it gives the most accurate result, but sucks dick. 20 minute test is nice and all, but sucks, 8 minutes hurts like a *****, sucks but at least i get it over with quickly (i've actually never used it, but i have a max 8 minute power
pr and it's pretty close to my ftp times 1.1)