I switched from bio 3/4 to psych 3/4 as well and it was probably the best decision I ever made. If you want to stick to bio 3/4, then by all means stick to it.. I don't know much about the course to say whether it's better than psych or not, but psych is so much more interesting. Also, in your sig it says you'll be doing chem as well, so if you really don't like bio and change to psych you're at no real disadvantage because chem's a pre-req subject for a lot of the courses that bio is as well, so look into that as well.
However, don't fall into the trap of thinking that it's easier to do well in - the thing is, most people that choose psych choose it out of interest, and are thus more inclined to do well in it as opposed to bio. I know a lot of my friends chose bio and didn't like it at all, and thus did a lot worse than they could have if they chose something they liked. So keep that in mind - if you enjoy the subject you'll love studying for it, and thus you're probably more likely to do well than if you didn't like the subject.
Good luck deciding!