Why not DFA 100 2.8 WR? Its built quality is superb. For macro, 100mm is more convenient IMHO. You will need that extra distance in case you want to use extension tube or close up filter for bigger magnification.
I had the DFA 50mm f/2.8 Macro and I would say it is good and sharp lens. Definitely like the Quick Shift feature. I use this focal length a lot for product shots. Macro isn't just about shooting bugs and there is definitely a place for the 50mm macro. Most modern macro lenses will go to 1:1 magnification, so choose your lens based on the angle of view and working distance to the subject.
I owned this lens before, and it's really sharp as SBC had indicated, and really good for flowers.
Snaps of it, very little processing from Picasa which wasn't really good but was what I know back then...
Having said that, I decided to only have 1 macro, and shrunk my collection of macros to just 1 - 100mm WR. Like what Denis said, decide on the angle of view and object distance, get the lens, and keep shooting with it.