hemvig,
The side channel utilizes a different type of flow in the pump's volute. As the impeller turns, the fluid rotations in a circular motion parallel to a the plane tangent to the impeller tip.
1. Side Channel Pumps have a fully open impeller, and it has been my experience that this is a less efficient pump.
2. The pumps I have experience with use impellers that are hydraulically balanced on the shaft in the axial direction. When you are operating somewhere on the curve, the pump runs great. However, if the pump is ever operated at shut off (or run out) the impellers will not be balanced and there will be large force pressing the impeller into the side of the case. Basically, you can burn up a pump rather easily.
3. Finally, I have only seen these pumps built with very cheap construction. They have a radially split design similar to a tie-rod multistage pump.
4. Advantages: It is a cheap pump and it can pump fluids with high % entrained gases.
If you have the budget, I would look more toward a BB3.