What's the scoop on trimming your horse's ear hair?
I have found clipped ears to be very common, across most disciplines, for show horses. It's standard operating procedure in the hunter rings. In some disciplines like dressage and jumping, it's also very common. There's also the school of thought that ear hair "was put there for a reason" and I agree with that, too. Luckily, you can have the best of both worlds if you want to tidy the ears and still leave some bug protection.
You can clip the ears are along the edges, which can be done by folding the ear like a taco and zipping your clippers along the edges. This presents a trimmed and tidy ear, and can also be accomplished with safety scissors for those horses that are sensitive to clippers buzzing around their ears. Most horse ears grow some wild and wooly hairs, especially near the bottom, and this trimming of the outside edge can clean them up.
Folding the ear like a taco lets you trim the edges. Using a super quiet and low vibration clipper like Wahl's KM10 helps, too.
Sometimes you may want to clip the inside of the ears. I find that the smaller clippers that have a very small blade are quiet and small enough to work well in the ears. This removes all natural bug and sun protection, so have a plan about how to manage this. A fly mask with ears worn during the day, and some fly spray (applied with your hand) can help during riding. You also have the option of using an ear bonnet while riding.
If you are worried about your horse tolerating clippers or their ears being handled, add this to your daily grooming routine a tiny bit at a time. Work on being able to touch the ears, then throw him a party with tons of praise. Eventually you will be able to work up to clippers turned on around his ears. It needs to be part of his life! Even if you don't clip the ears, you may find yourself in a pickle if there is an injury or cut/scrape that needs attention. Your patient groundwork in handling ears will pay off!
Might find that a smaller clipper is better for ears... easier to work with!
For my own horses, who live outside and don't go to shows, I prefer to leave the ear hair. It provides bug and sun protection and I rather like the fuzzy look. In either case, you will want to attend to your horse's ears to check for aural plaques, bug bites, and general health. Generally speaking, you won't need to clean your horse's ears, but instead pay attention to them, handle them daily, and watch for icky stuff.
Do you clip ear hair, leave it natural, or just trim the woolies?