Most HIV infections in the Western world are of subtype B. Most of the research that we have on HIV is also on subtype B, though it accounts for only about 12% of all global HIV infections. 
In contrast, less research is available for subtype C, although nearly 50% of all people living with HIV have subtype C.  It is very common in the high prevalence countries of Southern Africa, as well as in the horn of Africa and India.