Welcome to the Apple Discussions.
A lot depends on what you are studying and what you want the device to do for you.
The iPad is small and light and connects to the internet. Has a lot of handy apps available.
The MBA is small and light though not as much as the iPad. But can run a very large selection of software that you can not put on the iPad.
So a lot depends on what you want to do with the device.
Good advice is drop in at an Apple Retail store and try both units and see which feels better to you.
If you need any form of data input the MacBook Air is your best choice. The iPad is handy for web access and mail. Lot's of useful apps. Hopeless for anything unless minimal data entry.
If you need 3G access consider a 3G dongle or similar for the MBA.
I have an MBA and an iPad. Love them both but they are different animals.
Key to this is if you need to visit any flash website during the school term. If you do, then buy yourself a Macbook Air period. For 3G, get a MIFI device and skip the USB stick option.
There are a number of road blocks you'll have to face with the iPad if you want to do any serious work with it. One, you need a way to store/retreive your documents and the iOS system does not work the same way as a normal computer does. So you need to setup up a WebDAV server. Most high end NAS systems (Network Attached Storage) have a built-in WebDAV server. Otherwise, you need to pay Apple $99 for their iDisk (Mobile Me) option which can get pretty slow at times. The reason I mentioned WebDAV is because Pages, Numbers and Keynote use it. Otherwise, you'll need iTunes or iDisk to sync files which is not really convenient. Another stumbling block is setting a static IP address for your home WebDAV server. Again, this cost money. Pogoplug is another option to save files and print them to an HP color printer as well. I own that as well, but it only works as a file saving NAS (final proof), but will work in environments where there is a corporate IDS firewall in place like a SonicWall.
Then you need an external keyboard for typing essays.
If you add it all up, you're not saving very much compared to the 64Gb MBA 11". And that base model MBA is very quick loading webpages, loading OpenOffice etc..
Since I already own a fast Macbook myself, I settled for an iPad and for about 60% of the time, I can do without the Macbook on business trips. The other 40%, I'll bring both and leave one (usually my MB) at the hotel room.
Hope this helps.
I have used both a laptop for years and an iPad for months. For using around the home and carrying round during a full day I prefer the iPad for the following reasons:
No need to bring a power adapter for the full day
The supreme iPod. Great for listening to podcasts, music, iTunes U, YouTube.
Sound quality is excellent and I'm picky about that kind of thing.
Light weight and easy to flop down on a table (using a leather case with built in stand)
Can plop it by the sink while doing dishes
Can plop it by your bath tub
Light, easy to lie on a couch and read, surf, email
Virtual Typing is good, much easier than an iPhone. About 85% as easy compared to a keyboard. Pages has many features that I'm still impressed by and learning.
Nice to touch the computer, the Internet, to flip through things on a page. Track pad is not quite the same as touching the image and pinching etc.
I guess instead of starting a new thread I'll just add to this, I am in somewhat the same situation. I currently own a MBP 17" and really wanted to downsize for travel and leave the MBP at home. I have looked at going just Ipad, or MBA+Ipad to even trying a Mini. My Travel is a little different because I will be relocating for extended periods of time away from home. So I could set up a mini with monitor, or just an MBA or an MBA using an Ipad for extend screen relestate. My usage is mainly web and MS Office stuff so I wont need the horsepower of my MBP. The two main cons of the Ipad only is flash, and doing papers so trying to keep the cost down is driving me nuts.
Air is better.
Air is different, not necessarily "better".
iPad is only good for read book and watching video
So it doesn't do internet, create/edit/view presentations, spreadsheets & documents, email, drawing art, downloading and listening to music, controlling remote computers, tracking inventory, (and on and on and on).
I prefer to read book on my iphone
You prefer to read on a 3.5" display over a 9.7" display?
Guess that explains a lot...