Both of them have 2gb ram, ATI 9400 video adapter, unibody, glass screen, physical dimensions (except in depth). In fact, the only differences are:
1. Air is 3.0 lbs. Macbook is 4.5 lbs. (although by touch I thought the Air was half the weight)
2. Air is .76 inch thick. Macbook is .95 inch thick.
3. Air has 120gb hard drive, Macbook has 250gb hard drive.
4. Air has 1.6ghz (1.8 if you do a custom order) processor, Macbook has 2.4ghz.
5. Macbook has a new "glass" touchpad which I really liked a lot.
6. Macbook has physical ethernet plug and a 2nd USB port.
7. Macbook has integrated CDROM/DVD player.
8. Macbook can be upgraded to 4gb ram.
9. You can swap batteries on the Macbook.
I wanted the air. I really did. But in the end I was losing 1 lb and 1/5th of an inch, and a lot of flexibility.. I decided to have a beefier processor and 1lb more.
Post-Note: The new touchpad allows you to set the bottom right or bottom left of the touchpod to be the Right-Click area. Sweeet!