So were there good defenders at ZLMB? Or were the critics just able to trounce the believers because of a more open and free format?
It depends on the topic, in my opinion. Critics aren't more intelligent or "better" in some way than defenders of the faith are. It all has to do with what is being defended. I think defenders usually "win" in debates about whether or not Mormonism is a Christian faith, for example. And they can offer good evidence that Mormonism, as a social system, can be very helpful to many individuals (although they tend to ignore the potential harm, as well).
But in regards to other topics, the negative evidence is just so overwhelming (say, for example, Joseph Smith secretly marrying young women and other men's wives, or the Book of Abraham problems) that no amount of intelligence and diligence is going to make the defenders' argument look "good". So yes, in a more open and free format, they were regularly trounced in those sort of arguments.
I'm sure they would not agree. Perhaps they really felt that their arguments always looked better, and critics were just mean people, and that was what created the stress. Who knows. The human mind is amazing in its capacity for self-delusion. (maybe my own mind is deluding myself in terms of who looked "good"!)