Going back to what or not to wear after Labor Day I think is more common sense than fashion as far as cowboys. I would look pretty stupid mashing cows around in a snow storm with a palm leaf on, don't you think??? And I find it too hot in the summer to wear a felt. More or less it depends on the weather for me, not so much the holiday. And winters in NE Nevada are too cold for just wearing a felt hat. I usually wear a scotch cap, layers upon layers of clothes, wool coats, gloves, socks , scarves and insulated snow pak boots for almost 6 months out of the year.
I love my palm leaf hats I can thrash horses, nasty steers and my husband with them and they hold up.
I like a 5 inch brim for the shade, but I don't "taco" mine. I have a Seratelli 6X beaver for a cheap work hat and I am very surprised as how long it has held up. The number of "x"s for a quality of hat really depends on the maker. The best way to tell is just to feel them. One makers 20X may not be as high of quality as another. Also hats not only come in beaver fur, mink is the cat's meow in my opinion!
And not all custom hats are equal either. Someone mentioned Shorty's, she makes a real nice quality hat...well worth the $. My husband did some trading with a hat maker who really wanted a cheap mexican made reata. My husband set him a reata, and he built him a hat. The binding on the brim wasn't stitched properly nor was the hat blocked right. My husband wore it once and it lost it's shape...lesson learned. You get what you pay(or trade) for.
Speaking of binding, if you get a hat with a bound edge brim, be aware of how much moisture is used to shape it. Once the ribbon for the binding gets wet it shrinks considerably more so than the brim it is stitched to. This can causing rippling in the brim and ruining your hat.
As far as the shape, I think it depends on where you live and the occasion you wear hat for. Hats were meant to be functional. My palm leaf has a fairly flat brim but turned up a little on the sides for shade. I wear my felt hat in the spring and fall which can be windy in NV so I have the sides up and I cut a flap out in the back about 4 or inches long out of the sweat band. If you fold it out of the hat and pull your hat down tight with it helps keep it on the wind. I think this is why you see them west Texas boys with the tacoed hats. I imagine its probably easier it keep it on in the wind as opposed to a flat hat, which somewhat resembles a frisbee. lol