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
Leadership:
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
Research:
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>