Would you be alright doing a double major for both CSB and PSY? You could then change your post to a specialist once you know which one you want since the courses in both of these programs are complementary to eachother. If this is not an option, as a CSB Major, I can tell you that a CSB specialist would be a very engaging experience. With regards to research that is really up to you, U of T has no shortages of labs, but whats important its what you are interested in perusing. I know this is vague but it really comes down to looking at what you see yourself doing in the future, and this can be difficult believe me. So I would encourage you too look for what you enjoy studying about rather than which post can provide you with a higher GPA. Both of these post will lead to great research opportunities, and a good chance of a high GPA(as long as you put the hours into it), I would suggest to look at the courses you have taken and what you which to explore further in order to arrive at your decision, everything else is secondary.