Comparing MacBook Air sleep resume times
This is not an actual answer to your questions, but more information on the subject:

MacBook Airs go into "deep sleep" (hibernate) when left with the lid closed for a longer while. Basically, the current state of the machine is saved to the hard drive (the SSD in the case of MacBooks) and the machine turns off, thus not consuming any power while in standby. When you open the lid, the machine state is retrieved from the SSD and restored.

So, the wake time is determined by the speed of the SSD inside the MacBook Air.

2010 MacBook Airs have SSD speeds in terms of 100 MBps, while latest MacBook Airs (2012) have SSD speeds in terms of 400-500 MBps, so wake time should be a lot faster with the 2012 models.

Comparing with the iPad is irrelevant, as iPads do not hibernate, as far as I'm aware of.