Which prism has a greater surface area? 2 prisms. A rectangular prism has a length of 12 inches, height of 8 inches, and width of 6 inches. A triangular prism has a rectangular base with a length of 6 inches and height of 12 inches. 2 rectangular sides are 12 inches by 10 inches. The triangular sides have a base of 6 inches an height of 8 inches. The rectangular prism has a greater surface area by 72 square inches. The rectangular prism has a greater surface area by 88 square inches. The triangular prism has a greater surface area by 72 square inches. The triangular prism has a greater surface area by 88 square inches.