I was always of the belief that mino was somewhat stronger then doxy, more lipid soluble etc. This study is to do with MRSA staph which is common in alot of us with chronic sinusitis. In another study of adult patients with CA-MRSA infections, 54 percent (13/24) were treated with doxycycline and 46 percent (11/24) were treated with minocycline.25 Doxycycline achieved a 92-percent success rate as compared to a 73-percent success rate with minocycline. Based on microbiologic testing in vitro, doxycycline has also been shown to be a very potent agent against CA-MRSA strains with a minimum inhibitory concentration (MIC50 ) value of 0.25μg/mL This group of studies http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2923949/ which the above is included in is more about MRSA skin infections then sinusitis but i dont think it would be too off the mark. Doxy may not be as effective as mino for other infections but i havent really looked too deeply into this yet.