I think tunability in a given drum size depends on the setup. I want a 15" as my first floor tom mainly because most of the 14's I' ve tried and/or owned have not been able to take the lower tuning, but a 16 tuned to the same note would be too "timbale like" for my tastes. Now, to avoid the kind of tuning problems mentioned (1" differential), the whole range of drums will be 8, 10, 13, 15, and 18", which I think will yield a wide range of tones without having to set up like Nicko McBrain. I tend to regard odd sizes as a "plussed-up" version of the next size down anyway; 13's and 15's doing what 12's and 14's dare not try. If I could get 11 and 17" toms I would, just to see....