If you can only obtain one device, I would recommend getting a laptop. You need to be able to connect to your school's electronic resources/network in order to accomplish things like searching the library, literature searches, administrative tasks, etc. It is unlikely that all of those resources will be available via a mobile app so that they can be accessed via tablets. I would also urge you to analyze platform compatibility to see whether you will be able to do everything with an Apple device because that operating system has some serious deficits - like not being able to run any flash-based applications. Android tablets are much less expensive but just as versatile & have more free apps. If you really want a versatile but inexpensive tablet, consider the (Android) Kindle HD Fire - although it's native state is connection to the Amazon
marketplace, it can easily be configured to download & run general Android apps (Google play store) ... and, it's less than $300.
I realize that everyone is iPad crazy right now, but if you aren't able to use it for everything, it will just end up as a very expensive toy. If you do decide to purchase a tablet, go with the same platform as your phone (Android vs Apple) so you can access the same cloud storage & apps from either device.