1: screen.
IPad Air:9.7-inch retina display with 2048 x 1536 pixel resolution.
Ipad mini:7.9-inch retina display, 1024×768 pixel resolution.
2: Weight and specifications.
Ipad air: 240× 169.5× 7.5mm，453g。
Ipad mini: 200× 134.7× 7.5mm，33 1g。
3: Body color.
IPad Air: silver, space gray and black.
Ipad mini: there are only two colors: black and silver.
From the overall configuration, ipad air is cost-effective.