I would go for more, it will be less expensive to get it "out of the box" rather than upgrading down the road. 128GB is not much storage these days, with the bloated applications, and if you have pics, video (which takes up a lot, as well as your music. My experience has been you always end up using more than you think you will.
Hope this helps
As a uni student - you really don't need all that much space for your studies...
(unless of course you store the videos taken in lecutes etc.)
Generally 128 GB is on the low side - with pictures, music, movies & applications; however if you're really only talking about documents - a couple of years worth of work will easily fit into 10 GB - so this should be enough...