I second @RichInPitt ‘s comment that some people do better on one or the other. May not hurt to take. You can wait to send scores.
Your GC knows more than I do. But ACT says there are concordance tables generated by ACT and College Bpard that stakeholders can use to compare scores. From this, I would think colleges could make decisions based on either test score.
http://www.act.org/content/act/en/products-and-services/the-act/scores/act-sat-concordance.html