Although I am not so much involved on meta, I prefer the current Q&A format over the alternatives.
The main reason, for me, is that the Q&A format tends to lead to a relatively focused form of discussion, usually concentrated on the main relevant issues. In posting an answer, a participant is forced to articulate the best grounds for a given perspective. Thus, we tend to find essentially one or just a few well-written posts for each major position on the issue, and one can sensibly compare them. I find this more useful than the kind of meandering or overly discursive debate that one finds on a discussion board.
The feedback resulting from voting only adds to this, since not only can one see the various main positions, but also one can get a sense of the community on those issues. Thus, the voting feedback is an important secondary reason to keep the current meta.
The old discussion format, in contrast, tended to amplify the views of those who post loudly or often, rather than those who post well. I think that wasn't good for the community, and I personally didn't find it as useful as the current system.
So let's keep the current format, which I feel encourages people to find and articulate the best supporting arguments for their position, and which helps the community stay focused.