 
It's true, there really is nothing better for keeping the sun and rain off your head than a cowboy hat. The brim does a great job of casting shade around your face, and if you have a waterproof hat or cover for it, the rain slides down the brim and falls off well in front of you.
The drawbacks: Reality is, cowboy hats are hard to keep on your head! If they blow off while training a horse,they can spook the horse, which is really dangerous. Until my last year of training horses in California, I rarely wore a cowboy hat. I almost always wore a favorite baseball cap (and it was waterproof).
Yes, I know some dude hats come with strings. I would not be caught dead training a horse while wearing a hat with a string... or anything else tied around my neck that could get caught and choke me to death if the horse spooked or bucked.
Cowboy hats can also be knocked off easily if a horse swings his head and hits your hat, or you can swing your arm and knock it off yourself. (You can also bash it against your car door while getting in and out, as I have stupidly done several times.)
Their shape can spook any horse who isn't used to them, so I am always careful about approaching a strange horse while wearing one. It's one thing to wear a cowboy hat in a horse-show or rodeo, where nearly all the horses are used to them and you're riding a familiar horse. But going house-to-house training strange horses as I did (see the Cowgirl Image Website banner), was a different story.
The last year I trained horses full-time, I wore my cowboy hat every single time I trained a horse. Halter-Breaking, Saddle-Breaking, Jumping, Dressage -- I wore the hat. It made training difficult, because the more a horse acted-up, the more I had to remember to make sure my hat didn't blow off -- so I was distracted from the horse, which was dangerous.
But it was a good test of how effective a horse-trainer I was -- even while distracted by the hat, I still got through my horse-training sessions safely and made progress with the horses. Bottom line is... wear clothing and use equipment that is safe and practical while training horses. Save the flashy stuff for showing off.
Jeans are made of tough material. They rub against leather, get covered in dust and mud, get rained on, and still look fairly presentable after a good washing. They also last a while, depending on their quality and use.
I personally like boot-cut jeans, when I'm riding a horse and wearing cowboy boots but not chaps.
When I'm wearing chaps or half-chaps, I like an ankle-hugging jean-cut, so I can tuck them into my boots and zip my chaps without extra fabric getting in the way.

I love chaps! They are extremely practical. They save lots of money because you don't wear-out your jeans or boots as fast. They protect your legs from trees and brush. They keep your legs pretty dry when you're riding in rain. They keep your jeans clean.
The downside is that they are harder to walk in, and make it more difficult to mount and dismount. If they have fringes, they can scare any horse not used to them. And they are hot! Wearing them in 100+*F weather is not fun.
Half-Chaps are a good alternative when you just want to protect your calf area, or keep your boots clean (my #1 reason). Horses don't notice them - they accept them as part of your boot. You can easily mount and dismount while wearing them.
The main downside of half-chaps is that you must buckle your spurs over the top of them, which is rather annoying and requires a bit larger spur-strap. But hey, nothing's perfect. |