Which is better for Dog agility course? 3/8" or 1/2"

It depends on the specific needs and conditions of the dog course. In general, a thicker rubber roll (such as the 1/2" Mega Rubber Roll) would provide more cushioning and durability, which may be beneficial for dogs with joint issues or for courses that see heavy use. However, a thinner rubber roll (such as the 3/8" Heavy Duty Rubber Roll) would be lighter and easier to transport and install, which may be more convenient for some uses. Ultimately, the best option would depend on the specific needs and requirements of the course and the dogs using it.