The eco clamp is the cheaper option, however you may be slightly restricted by the clamping distance, thicker surfaces will require the heavy duty clamp. The eco clamp can span 30mm or 1.18 inches and is suitable for tubular and square tubes.
The heavy duty clamp is… heavy duty! It can span a further distance, to 55mm or 2.17 inches. The heavy duty clamp is capable of higher torque therefore a tighter grip on surfaces. There is a small insert that can convert the clamp’s feet from a flat, to a V shape, accommodating flat surfaces and circular tubes respectively. The insert is located on the back of the clamp and can be removed by unscrewing the black handwheel.