The Air is fully WiFi capable so that is not an issue.
The iPad and Air are very different concepts...the only apps you can put on the iPad are those from the app store or certain other sources. The apps such as Pages while compatible with MS Word, are much more limited in capbility than those you can install on the Air. The iPad is very portable in comparison, though the Air is itself very portable.
The Air can have any Mac OS X compatible software installed. The Air has a normal keyboard which is much easier to type on than the virtual keyboard. The Air has a larger screen and can attach to peripherals.
The Air costs more, is larger and heavier, but has much more capability and flexibility.
Depending on your full usage, and is this your only computer, if so the Air would be a better choice.