This seems like a great stove system, however for wood burning I think I would still stick with the firefly. It looks like any additional wood added to the Caldera would have to be done from the top correct? taking the pot on and off to add sticks is not as good a design as the side port option on the firefly. Waiting for a bed of coals is also a negative in my opinion of course. Others have pointed out soot is an issue too. The firefly is a clean burner much like the emberlit in that regard.
IF I was going alcohol or Nesbit, it would seem the Caldera has the advantage over the firefly... but seeing as those fuel sources are my second choice, I would be better off with the firefly design than I would be with the Caldera.
The resons would be that using the firefly for wood would be easier in terms of adding more wood to the fire, more control of the amount of heat,and the volume savings in my pack.
Of course, I fully get that my criteria is not the same as everyone else's and this is all opinion, but there is my two cents worth.