RR is for the higher probabilities and OR is for the smaller one to show an association between events
Also according to Cochrane´s Handbook, when dealing with very rare frequencies of events in at least one of the groups (n=0) it is recommended to calculate odds ratio with Peto method http://handbook.cochrane.org/chapter_9/9_4_4_2_peto_odds_ratio_method.htm
Chapter 5 in Joe Hilbe's book Logistic Regression Models provides one of the best explanations on this topic.
Qatar University & Birzeit University
Indian Council of Medical Research
University of Nottingham
University Clinical Hospital Center "Sestre Milosrdnice"
Geoffrey Chima Nwakwuo
Community Initiative for Infectious Disease Control (CIIDC), Nigeria
Hassan Ali Abdelwahid
Suez Canal University
Pwaveno H. Bamaiyi
University of Malaysia, Kelantan
Palacký University of Olomouc