Selectivity refers to qualifications of the applicants. Competitiveness refers to the number of applicants per available seats. The difficulty for an individual to achieve GPA/MCAT for MD acceptance is what most applicants mean when they say "harder" for a student to get accepted to MD school. That is selectivity; it is not competitiveness
On a selectivity basis (GPA/MCAT) yes, MD have higher GPA/MCAT as a pool of applicants. Thus MD is more selective
On a Applicant to Seat Ratio, the DO pool has more applicants per available seat. Thus DO is more competitive
41% of MD applicants matriculate in the cycle that they apply with 2.43 applicants per seat (roughly 2 in 5 who apply start MD school)
36% of DO applicants matriculate in the cycle that they apply with 2.78 applicants per seat (roughly 1 in 3 who apply start DO school)
see my previous post for numbers
http://forums.studentdoctor.net/threads/do-seems-way-more-competitive.1141763/#post-16560821