I'm doing spesh,psych, biol and did methods last year.
If you really enjoy biol, you'll probably enjoy unit 3 psych where you learn about sleep and the brain. Psych is more content heavy, with huge emphasis on research methods. (Aim, hypothesis, extraneous variables... You'll probably going to write a research report throughout the year) And you are looking at things from a more psychological rather than biological perspective (lol pretty obvious)
A lot of memorising.. Concepts are easier than biol, but there are small parts of the course that are pretty dry.
You need to know your definitions, and have a lot of practise with your wording, when answering questions, as examiners are picky with how you word your responses (like biol)
Spesh and methods complement each other wonderfully. I mean the two subjects are like 1.5 if you do them together, as there's heaps of overlap.
It's your choice. If you are passionate about psych, go for it.
Spesh scales a lot. But you need to also want to do it. (Don't just do it for the score)
Don't be intimated by the subject. I'm pretty average at math, but with practise it becomes a lot more easier.
Regardless of what subject you do, you'll do very well if you put in the effort.
Although if you are pretty good at math, I think it's a lot easier to score higher in spesh.
According to last year, 35 in spesh is like 48 in psych.