I agree if you are just doing one horse the Oster A5 is a great clipper. Lots of torque to get through that thick coat. I would buy at least 2 if not 3 extra blades. The clipper blades heat up and you can "clipper burn" your horse if you are not changing out the blade. Every couple of minutes touch the flat top of the blade to your arm. If it's too hot for you it's too hot for them. When you take off one blade to cool brush the hair/dirt off with an old toothbrush and oil it between the blade and the cutter. This will make your blades last 100% longer. If you just keep clipping until the blade heats up, gets clogged with dirt and hair, and gives up you will be wasting a lot of money on getting blades sharpened and buying new blades.
Riding: The art of keeping a horse between you and the ground. ~Author Unknown