They are mostly the same, except for the science stream, you're required to take at least first year maths. Apart from those maths units, all psychology classes will consist of those studying it from B. Arts, B. Science and B. Psychology.
For psychology majors, it really depends on what you're interested in outside of psychology. For example, seeing as though you did 4U maths, it might interested you to take a minor in maths or stats from B. Sci. (Neuroscience is a popular combination with psychology.) From B. Arts, you would need to fill up your degree with arts units instead, alongside your psychology major. (Philosophy is also a popular combination with psychology.)
For students under the Bachelor of Psychology degree, an honours year is a requirement, whereas it is optional for those under B. Arts or B. Science.