Depends if you intend on doing a masters in psychology (e.g. clinical org forensics). If you do you need to get invited into honours before hand from either a B.Psych, B.Psych Sci, B Adv Sci (Psych) or B Sci (Psych) iirc, dont think you can do it through arts not sure - someone confirm. Seriously, B. Psych doesn't really give you a advantage over the other courses cause everyone needs a D+ (in psych cores) to get invited its just the prestige attached to its name (from my experience)