Upload & Sell: On
You have to look at the devices for what they are. The iPad is NOT an laptop replacement. It cannot install regular programs. You cannot therefore do major editing.
The iPad is brilliant at being a lightweight machine for viewing the Web, email, watching Movies and podcasts, and Viewing images. Yes there are apps that allow you to do editing in a minor way. You cannot import images directly to a folder structure as you would normally do. I would not use it to store images directly. It is very portable and the battery life is great. I take mine with me all the time.
The MacBook Air is a lightweight laptop. All the current ones are very fast. They will also run all the normal applications such as Aperture, Lightroom and Photoshop and will handle RAW files. Processing times are not that bad. In my opinion, if you want to store files then get the Air along with an external drive.
I'm coming from a late 2008 MBP, planning to get a 13" 2012 MacBook Air as my primary computer. I'll be mating it with a Thunderbolt display at home. I do the vast majority of my editing in LR4. It seems that going with the i7 and 8GB of RAM is the way to go if I want to get the most life out of this machine, which I'd plan to use for the next 3-4 years. I have a question regarding the SSD option. Does the 512GB version offer any performance advantage over the 256GB version presuming I keep the drives as empty as possible? I like to import RAWs to the laptop, work on them, and then move them to external drives for the long-term.
As to the original topic, I agree with everyone. I have the original iPad and new iPad, and they're really only good for jpeg uploads and some modifications in Snapseed if I want to post something to Facebook or something. It's also a fun way to view photos while travelling if you don't have a laptop.