Not to answer with a question, but, if you could get one for free right now which one would it be and why would you choose it? Your answer would be my answer to your question.
All jokes aside, either one will work. Being a dedicated ACR forum means you'll probably get more points toward the ACR of course but the only thing I can honestly say against an ACR is that it is still fairly new and BM hasn't developed its groove yet. It's a new platform without the benefit of years of folks working with it.