Unfortunately, this is the kind of topic that so often turns acrimonious here. There was a thread not too long ago that asserted ammonium bromide was a "crutch". Could never figure out why (except maybe because it works so well in an emulsion??) Anyway, no substantiation to the claim. Just an assertion.
Jason, perhaps the best way for you to answer the question is to try different bromides. You know where to find a proven ammonium recipe . http://thelightfarm.com/cgi-bin/html...tent=15Jun2013.
I, in turn, will refrain from speculation on sodium bromide, as I haven't yet tried it. It's the real paradox of these kinds of discussions. It is natural to want to speculate, but it really serves no purpose. So, you are left with people who have actual experience, and in our case, there aren't that many emulsion makers yet. There wouldn't be much of a discussion among the few of us, but we can hope and encourage others to take the plunge.