Hi Water, All!
Avna is spot on; you simply have to keep trying on different helmets until you find The One. Try them _all_; pick the best.
Remember, you will often be wearing it for hours at a stretch, and frequently your head will be in constant movement. My first, second, and third considerations would be fit, fit, and FIT. The helmet should be snug, but comfortable, and should not move when you nod your head vigorously. Otherwise, the first time you hit a trot, the brim of the helmet will slide down on your nose blocking your vision; not good. Then, it should offer good ventilation, or it will soon be filled with sweat. It should have an absorbent sweat band, or the sweat will soon be in your eyes. Coming in something like tenth on this non-linear scale, is style. 'Nuff said about style; they're _all_ ugly . . . ;-)
And try the helmet on _first_, then look at the price tag. An expensive helmet on your head is much preferred over a cheap one that hangs on a hook in your tack room because it's uncomfortable to wear. Ask yourself just how much your cabeza is worth.
I would suggest finding a large tack store that actually stocks a wide selection of different helmets, even if you have to make a pilgrimage to get to it. We have a Dover Saddlery store about an hour's drive away that is quite good, and recommendable if you have one within reasonable driving distance; otherwise you'll have to ask around, or start making calls.
That said, I really like my Charles Owens GR8, and when time comes for a new one, it will take something pretty special to win me over this model.
Steve Jernigan KG0MB
University of Colorado