Do ACT Subscores Matter for SAT Conversion?

How much do Math and English ACT subscores matter when approximating your SAT score from your ACT score?

For example, does getting a 30 with subscores of E: 33 M:32 R: 28 S: 28 look better than getting a 30 with subscores of E: 27 M: 27 R: 28 S: 36? I know that a 30 on the ACT is around a 2000 on the old SAT, but how much can high English and Math subscores alter that? Is getting a couple of higher subscores and a couple of lower ones better than having "well-rounded" ACT subscores?

Math and English subscores do not matter when it comes to comparing ACT and SAT scores. There are no conversion charts yet for the current SAT, but for the old out-of-2400 SAT, the only relevant information used to convert ACT scores to SAT scores was the composite ACT score. According to these charts, a 30 composite score would've been equivalent to about a 2000 SAT score.

The only reasons you'd want to have higher subscores in certain areas would be if you're applying to a specialized program (like engineering school) that might, for instance, value Math and Science scores more than Reading and English scores, or if you're applying to a school that superscores the ACT. Otherwise, colleges are going to look at your composite and section scores.