I think I would opt for the doxycycline over azythromycin. Doxycycline can pass the blood brain barrier.
Bacteriostatic azithromycin stops the pneumonic airborne infection within lung tissue and utilizes existing immunity in a subject. Doxycycline is a waste of time and does not have the spectrum. Not to mention was not the agent used in the major trials on the combination therapy that are published.