Yes volume numbers are more "accurate".
The oz /ft are quick and dirty -but if one throws in the area- it all makes sense.
Frankly -I have found that 90% of all the airfoil stuff for model aerobats is just whimsy- in fact -I have tried same exact wing area and weight -with different airfoils - thick thinner 14%-11% etc- and if one really did not have one to compare against the other - it would be hard -if not impossible to know which wing was on the plane.
The full scale aircraft "engineers" will argue this -but most don't have any practical experience in models of the size we use in the weights we deal with and in the performance envelope we fly in.
Not to say that the text book larnin is not necessary!- it does work for a lot of stuff - mostly in full scale applications.