Since you said you get A's/A+'s with history I'd probably advise you stick with it, rather then taking a random chance with a hard subject like biology, which you might end up despising. In all seriousness, I'd say stick with history.. It's probably going to be more rote required than biology because biology is all applying!
Do psychology/bm if you want more rote style subjects.
Psych definitely won't be rote in 2011. In fact both the 2010 exams required a considerable amount of application. This is due to new exam writers who got hired in 2010 and were instructed to make exams which tested a person's understanding of the material rather than ability to memorise info. P.s. Psych is very competitive, although I highly recommend it cos it's awesome

Even though a subject may be about memorising (psych + bio) doesn't mean memorising everything will guarantee you a high score. It's kinda silly to assume something like that

It's about knowing how to write good answers in the exam, really understanding all aspects of the course instead of just memorising it and also really enjoying the subject because it'll help you to study more and put more effort in!
DarkVisor, stick with history. Unless you really don't like it. Rote subjects can be just as hard, if not harder, to get a very high score in (One person I know said she put equal effort and felt equally confident in revs and psych and got 38 in revs and 31 in psych. So some people don't do as well in "rote" subjects). Seeing as you're getting A/A+ in history why stop?