I guess I'm one of those dinosaurs that throw a 16, but I used to throw a 15. Two years ago, my coach moved me up to a 16 to try to slow me down, and keep me from throwing it to the arrows, and it seems to have worked. In all honesty though, the 15 was just to light. As far as having 16's in stock, well I usually have to have them order them for me. Talking about hitting power, I couldn't say if it's better or not, but I would recomend being able to handle the weight of the ball if you're going to throw it. I see to many people trying to throw a 16 that have a hard time just picking it up.
As for the brands I could care less about name, I like to choose a ball that I think will suite me. I currently use Motiv--- Cruel, SR2, and Recon(orange), Roto Grip--- Mars, Mutant Cell, Brunswick---- Ultra Zone, and a plastic, and 900 Global--- lunatic. In the past I've used Ebonite, and Storm, and have nothing against them, they were great balls . I think the bottom line would be knowing what you want the ball to do, and finding one you like to do it. Good luck choosing.