I know some people who like the Queen Square better than the Troemner because they feel it allows them to guage more sensitively changing reflexes and the like. Really, I've found that any hammer that has either more length or more heft than the Taylor makes reflexes much easier. It's a matter of taste beyond that.
The only thing I don't like about the Troemner is that the small end is too small; if I want to hit an individual muscle that small, I use my finger to guide me.