I'm a current graduate student
And have used a full sized iPad since its debut in 2010. It has been an incredible asset to my studies--even for the ability to deal with PDFs alone--and I've bought each successive new model (except for the fourth generation) and will continue to do so.
There is no way in hell you could convince me to go with the mini (although it clearly works for some) because the size of the 9.7 screen allows me to read, annotate, take notes, and even create/edit documents when necessary without much constraint. The mini, however, would never suffice for me personally.
My advice to you is to purchase a refurbished 3rd generation iPad from the Apple Store, because the retina display has made worlds of difference for me in terms of reading clarity and eye strain. This is just my 2 cents worth, of course, and I wish you much luck and success with your studies, regardless!