Hey, I'm currently doing both vector calculus and real analysis. I decided to do them both in my first year and I found real analysis much harder than vector calculus. Vector calculus is pretty much dealing with integrals in ~15 different ways. You really won't learn anything new, just new ways to apply what you already know. Real analysis is pretty much learning maths from scratch, properly. You will learn the definitions of things you never thought even needed to be defined, you will learn to do proofs for major concepts that in the past you have just took the lecturers word for being correct. It's not an insanely difficult subject, but I did fairly well in calcII and linear (93,82) and managed to fail an assignment(luckily only worth 3%). And I have also acknowledged that I will not be shooting for a H1 in this subject. I don't think that doing one before the other is really better, maybe doing one per semester would be a good idea though as they don't compliment each other and take quite a bit of study.