My belief is that you should take both the SAT and ACT. My daughter also received a disappointing SAT score (1320), which leaves her out of the running for merit scholarships at the two main schools she is looking at, although she has a high GPA, and should probably still be able to get into both colleges. However, with the 30 she received on her first try at the ACT, she is eligible for merit scholarships at both schools and her likelihood of getting accepted shoots up. The main difference for her was the Science component. Like you, she plans to major in Biology (or Biology/Biochemistry) as a pre-med major. She has a high aptitude for Science and that most assuredly helped her when she took the ACT. She also scored better in the Math area on the ACT. I would love to hear how things go if you do take the ACT. Please post an update.
Edited to add: A 1310 is a very good score by the way. Probably not enough for Ivy League, but strong enough to get you into most universities in the United States and you did better than most. I wanted to make sure you understand this!