I find it hard to vote as the 11" Air is probably too small for me as a primary machine. I wouldn't touch the high end iPad either though as i dont need that much storage space or 3g. I stream everything. And can tether to a mobile.
But looking at the options you have given i would choose the Air simply because the fully specced out iPad is overkill IMO, and as my iMac needs replacing the iPad wouldn't work as my only machine.
But looking at the options you have given i would choose the Air simply because the fully specced out iPad is overkill IMO, and as my iMac needs replacing the iPad wouldn't work as my only machine.