Hello,
The answer is that it depends. There are a lot of factors that come into play (e.g. grades, essays, extra-curriculars, majors, etc.), but perhaps the most important is whether or not that school is a fit for you. As much as it is your choice, I do feel obligated to equip you with ALL the facts and put your decision into perspective:
When you choose to do REA, you are foregoing your Early Decision 1 as well as ANY Early Action schools. That requires a strong commitment to that decision as well as a few considerations:
1) Profile quality: Colleges that offer REA are aware of the stakes at hand when it comes to your decision, and are more than willing to compensate for that fact. They will scrutinize EVERY detail. If you feel your personal statements, supplemental essays, your grades, your extracurriculars, or any part of your application maybe slightly lacking, they will catch onto that. Remember: they are comparing you to the some of the best applicants in the world, meaning all the Malala Yousefzais, the kids who discovered a new dinosaur species at 16, the kids who created biodegradable plastic bags out of seaweed at age 9...the point is, they can afford to be highly selective.
2) Compounded work: because you decided to fill only 1 application, in the event that you get deferred or rejected, you now have to fill out a multitude of applications on top of curriculum work (including all your IAs and IB coursework) — a workload that could have been saved had you done EA and ED. Again, this is not to discourage you from making that choice, if you believe you can handle the workload, but something to take into consideration as you approach the second semester of senior year.
At the end of the day, it is up to you — are you willing to take that risk for the chance at a reward?
Yours sincerely,
Dear Letterbox