In short, I haven't used either one nor dried my own produce, though many do so to improve their backpacking cuisine. Nevertheless I, as a consumer and a guy, feel completely qualified to pass judgment on these products solely on the basis of the following attributes: name, power, and overall Coolness Factor.
Name is no contest. Any guy would want his food dehydrator to have a manly, Arthurian name such as Excalibur, rather than the mundane-sounding American Harvest Dehydrator. I mean, c'monthat's the best they can do? Why not the Food Blaster?
As for power, more is always better. The American Harvest machine has a 1000-watt heater and 2400-rpm motor. Pretty impressive: squeezes moisture out of an apple slice like stepping on a wet sponge. The Excalibur model comes with a 400- or 600-watt heater. Hmmm. Advantage American Harvest, right? Maybe not. The Excalibur boasts a Parallex Horizontal Airflow. How cool is that? Call this one a draw.
Coolness Factor? Tough to judge; these are food dehydrators, after all. But clearly, considering the case thus far, the Excalibur wins on the basis of its name and cool-sounding airflow system. Plus, from a practical standpoint, I think its square design is more efficient: it stores more easily and probably holds more drying food on a per-square-inch basis. Round is not a very efficient shape.
So there. Is that insight, or what?