Our DS took both, only 1X for the ACT because it beat his 2 tries on the SAT. He had a 1390 out of 1600 for the SAT, and it was a 33 or 34 on the ACT. The ACT is different. Our DD also took both, but for her the SAT (1290) was a much better score than her ACT (25)(she didn't apply to the AFA), just illustrating the fact that 2 kids in one family performed differently on each test. The main reason why the ACT hurt her, but helped her brother is IMHO the ACT is really more geared to the Math and Science section. It is a composite score, so if you bomb one section it can hurt you. She bombed the science portion, if that one portion was not included she would have had a 29. The science portion is a lot of graphing and spatial awareness.
Additionally, google the class of 14 and you will be able to see what the median scores were for each. You always want to be in the median, if not above it. I know a few yrs back it was 680M and 650 CR