Which test score should I use?

I received a 31 on my ACT
English 31
Math 26
Reading 34
Science 34

and a 2110 on my SAT
Critical Reading 750
Math 660
Writing 700

I would like to apply to Northwestern or University of Chicago as reach schools and was wondering which score I should submit. I received an 8 on the writing section of the ACT but my composite score that time was a 30