SAT vs ACT and preparation

<p>Okay so I have taken the SATs twice and the ACT once. The SAT as a sophomore in March and a junior in December. Also the ACT this past February. My March scores for SAT were 560 W 550 CR and 690 M. My December scores were 520 W 640 CR and 710 M. My ACTs were a 26 composite with a 31 M 25 S 23 E 23 CR 9 on my essay. My question is based on these scores which test would be best for me to take again. I plan on taking one more standardized test. I preferred the SAT and didn't feel as rushed during it.
Also all three of these test scores were accomplished without a day of preparation/studying. This next time I plan on studying an extreme amount. My next test dates I can do are June 7th and the first fall dates of next year. I also have subject tests to take which based on practice tests I will do well on. what is the best way to excel at my writing and critical reading sections. My math is a matter of paying attention to details to get an 800. I would be happy with anything over 600 preferably closer to 700 on writing and 700s for critical reading which is only 60 points more. Any thoughts an ideas? I have an SAT official study guide from college board and an iPhone that can download study apps. What books should I read to prepare? Thanks for any advice you can give.</p>