Knowing the resistance is nice but there are other factors at play as well. The motor itself has an internal resistance, and not every fan is the same.
Based off of that, if you want a slightly more accurate comparison, you might want to grab a tachometer and try finding the rpm of your blade - that could give you a sort of guesstimate of performance.
"I am among those who think that science has great beauty. A scientist in his laboratory is not only a technician: he is also a child placed before natural phenomena which impress him like a fairy tale." - Marie Curie