Did both A2 and in quick summary
Maths - Easy, light revision which doesnt take a lot of your time. However the exam can be very unpredictable and even if you do well in past papers, the real exam paper can easily slip you up. Grade boundaries are usually quite consistent with AS in comparison to Psychology where the boundaries are fairly low.
Psychology - Quite tedious revision in that you basically just learn essays largely, however generally its not very difficult at all. Fortunately the exam is a lot more predictable, such as Unit 3 Aqa - Theres like 18 possible questions and thats it - No bs whatsoever.
I ended with an A* in psycho and kind of scraping an A in maths. During the year i definitely spent more time on maths so i was fully comfortable of the techniques and shizzles, however during exam season Psycho definitely took more time. If you have a slightly crappy Psycho teacher though, it can make A2 slightly tricky whereas for maths you can get away with it.