I don't have any experience with either. The airdesk looks like it's not worth the price. You could probably make the same thing yourself with a trip to the hardware store. The pro desk looks like its using components very similar to the Ram Mount, especially the tray but would at least be worth the money.
I think it depends on the laptop you plan to mount on it. These mounts might be fine for a netbook. But you would need a heavier duty one for a rugged or even just a heavier laptop.
Not sure what your budget is, but have you checked with a Jotto Desk or Ram Mounts dealer (using a phone call, not a Google search)? The pricing should be pretty similar (a bit more, but far better products/support) and the products will be better engineered and worth more if you decide to sell it later.