GRE subject test- Biology or Cell/Biochemistry?
This is a question best answered by the admissions officers at the programs to which you want to apply. They will generally have recommendations as to which test they would prefer you to take. If there's a consensus that one of the tests is preferable to the other, that's the one that you should take. 

(My particular sense on this is that Cell/Biochemistry is probably closer to what is expected for people in Computational Biology than the more general Biology exam. However, I am not a bio person, so I'm not speaking from a position of authority here.)