I have both an iPad and a laptop, and I bring my iPad to university almost exclusively. I find my laptop is a bit heavy and cumbersome, and the iPad allows me to type or draw or annotate PDFs, which is everything I'd need to do in a lecture. It's also easier than a laptop if you want to be productive on buses or trains, and has a far longer battery than my laptop. I take it with me everywhere in my handbag, and it's almost replaced my laptop for travel as well.
I'd say to get one if you're looking for something light and portable but with all the functions you'll need in a classroom. That said, if you don't have easy access to an actual computer and can only buy one device, an iPad can't replace all the functions of a laptop, especially when it comes to writing essays and that sort of thing.
As to whether to get an iPad or another tablet, that depends what kind of OS you prefer. If you're using an iPhone or a Mac already, you know how to use an iPad. If you're using an Android phone, you might prefer another tablet. If you aren't familiar with either, maybe have a bit of a play with a couple of tablets at a store or read some reviews and see which one you like.
