Is it best to groom before or after a ride and why?

Answer: BOTH

Before you ride, you want to get off the caked on dirt off to prevent sickness such as saddle sores.

After you ride, you want to go over your horse one last time, either with brushes, a hose or sponging your horse. During this period, you can see if your horse has any sores and such.

Have you ever noticed that most of the things we do for horses is to prevent sickness? ?:/