Chances of being accepted to UM

<p>As early decision deadlines approach, I'm stuck in a dilemma whether to apply to early decision or regular decision. My transcript/resume is as follows:
GPA: 4.1
Rank: 10/304
Secretary of National Honor Society(NHS) my junior year
Incumbent Vice President of NHS
Varsity Tennis captain
JV baseball captain
Founder and president of the medical club
Lab assistant at Taubman Biomedical Research Center
Did environmental research on breeding of the American toad at local vernal pool. I submitted my research and data to NASA'S Globe program and was 1 or 3 USA teams chosen to represent the nation at an international science program in New Delhi, India.
ACT: 26 composite(highest sub score was reading 31).
Let's be frank, my act score is rather extremely low. There's one more retake on December, and I plan to take it.
I have over 400 hours of volunteering service
I'm an AP Scholar with honor</p>

<p>I'm curious to whether I should wait until RD instead of ED and retake my ACT to increase my chances of being accepted in UM. Also, what are my chances of being accepted of I where to apply to ED? I am curious to what you guys say! Thank you.</p>