In an educational environment, you're the most important tool.
AutoCAD works on both platforms, choose which one you like more and use it. If you give an educationally-challenged person a MBP or a Windows laptop, they won't do any better or worst with the other. I use MBP because of less viruses and potential to get viruses [believe me, there still are Mac viruses].
If you're going to use AutoCAD, I recommend getting a very high-end computer to reduce lag [I'm not going to lie; I've never used AutoCAD, I'm a pre-med / bio student].
Get an external HDD [or an SSD if you have the money] to place all of your files on, and make back-ups on another secure computer reguarly. I have back-ups of my work on 3 different computers at my house and one online back-up in case they all burn out.
It's all up to you. If you want to future proof your rMBP, and you have the money, go all out and max out your MBP [the ~750GB SSD and the 16GB RAM]. Obviously, not everyone can do this, so I'd go with the 256GB and get an external SSD/HDD.