I would say that they are equally important. A college wants you to have good grades and good test scores. However, if you start high school with sort of crappy grades but show great improvement each year, that looks good. It's hard to give a good answer but you really should focus on doing well in each category.
Also don't forget that extracurriculars play a relatively important role in college admissions. Imo it would look better to be a good student with poor extracurriculars than a bad student with lots of extracurriculars. But like with grades and test scores, try to be well-rounded.