You need to put context or qualification around your question. How does it compare ? As a general guide - fluidized bed roasters typically have smaller batch sizes and much shorter batch times. They can require more effort to control given the higher operating temp and would normally undertake a shorter roast cycle - in other words, you really don't have a lot of margin (or time) for error. A batch time of 6 - 8 mins can be very quick. What they lose in batch capacity, they make up in more batches per hour. Fluidized bed roasters have a slightly lower yield per kilo compared to drum roasters as the roasted beans tend to lose a fraction more moisture and are "puffier" in roasted appearance. This is a direct result of higher air temps used to perform the roasting. Too much is written by fluidized bed roaster owners about how their methods result in a cleaner cup compared to drum - IMHO this is a typical marketing-BS statement perpetuated by FBR owners to exert their superiority over drum roasting equipment. A well setup, double-walled cast iron drum roaster can perform equally as well, if not better in the hands of an expert. The differentiating factors are generally the skill of the operator and the effectiveness of the setup. Both are more important than functional differences in roasting technology. Is a Ferrari F1 better than a Renault F1, a McLaren F1 or is it the way in which the cars are setup and the skill of the driver in exploiting the capabilities ? Sometimes a drum roaster is not a drum roaster. Case in point - my Joper might look like a drum roaster, but it is more like a fluidized bed than a drum roaster - it has a large, specially designed fan forced oven that runs super-heated air at almost 600 degrees C through an open end of the drum and does not rely on heating the drum surface for thermal transfer. The drum is only for agitation purposes - it is actually a 100% hot air roaster using a primary form of convection rather than conduction that is more traditionally implemented on many types of drum roasting equipment. Also be aware that one of the older and larger FBR manufacturers has recently stop manufacturing their equipment - so purchasing used equipment may come with added risks.
