For the sake of argument, if you have a netbook already, there's an interesting arrangement that works for me.
I support a web-app that only runs on IE (don't get me started, I've already fought that battle and lost). This is the only thing keeping me from doing my work entirely on my iPad. Until I set up LogMeIn on the laptop at work, and use the LogMeIn app for the iPad. Now I can access that app that few times I need to.
Everything else I need to do, I can do on the iPad. I can use the iWork apps to write MSOffice compatible documents, I can use iCloud to share all of that between my devices (iPhone and Mac mini). If I plan on doing a lot of typing, I can use the Apple Wireless Keyboard I have for my Mac mini. (My wife uses our keyboard with her iPad to take meeting minutes at work, recording the meeting with Voice Recorder on her iPhone.) I get my email on my iPad, voicemails from work are emailed, I can call out with Skype (and a USB headset connected with the Camera Connection Kit) ... I have yet to find something I can't do when I've needed to.
That said, in an academic setting, if they have some specialized software that you need (for example, Mathmatica or the like), then I can understand needing a full laptop. But I've found the iPad to be very capable out in the world. Your mileage may vary, of course. The SAFE bet is to get the Macbook Air, since you shouldn't have a problem running anything you need. If cost is a concern, you might be surprised exactly how much you can get done with an iPad. If you find you need to get the Air, get the most expensive on you can afford. You can't upgrade anything in the Air after the fact, save for adding an SDXC card for additional storage.