The stats I looked at showed the CX-5 with AWD at 3,560, which is heavier than the Mazda5.
The CX-5 without AWD is 3,290 or around there. The Mazda5 is 3417-50 for 2015 but lower in earlier years ('06-'11).
RE: aerodynamics, I don't think the mpg tests factor in cd, I dunno, aren't they on a...