I will say one advantage that the HotTop has over the Behmor is the ability to roast up to one pound of coffee at a time. It will roast in increments of 1/4lb, 1/2lb, or 1lb.
Also, the HotTop has a cooling tray, whereas the Behmor must cool down in the barrel. This can be problematic as the coffee will continue to roast for the next two minutes during the "cool down" phase on the Behmor. The cooling tray on the HotTop means that when you drop the beans, that is their roast profile.
There is some really good info about this at sweetmarias.com or on the home roasting forum at Home-Barista.com.