Is it just the pump size?
There are a few more differences than just the pump size. All three have different riffle designs and combination of materials within the sluice box for different configurations.
The 500 (Beach) model, has a ¼” primary classifier, with ¼” raised expanded material, combined with a round rod riffles system. To be used with smaller material (Beach Sand) and has a ribbed rubber matting. Measures 23” long.
The 800 model has a ½” primary classifier, with ½” raised expanded material, combined with a flat riffle design system. To be used with ¼” classified material, but will classify to ½” and has our rubber-backed black ribbed carpet, combined our black “moss” carpet. Measures 23 “ long.
The 1200 model has the same primary classifier, with ½” raised expanded, but comes with a drop riffle, or “Hungarian” design riffle. Which creates a much larger eddy behind the riffles and is 28 “ long. This too has the Black Carpet.