Hardest: The degree I'm doing
Easiest: The degree I'm doing
It's the only one I can mention, seeing as I haven't ever done another degree, so I wouldn't know.
Unless someone has done every degree possible, to compare it, then I don't think anyone can really say. Also, I'm sure there's no need to mention this next point, since it's fairly obvious, but everyone has their different strengths and weaknesses, so if someone finds Maths/Science related subjects fairly easy, they mght struggle with more essay based subjects such as humanities or languages. It's all subjective.