Pros : This fid/burnisher is the only one I've used in 16 years of stained glasswork. Easy to hold, somewhat flexible and just stiff enough to get the job done. Your soldering is only as good as your foiling and this fid is a perfect way to smooth good foil technique. I've never snapped one either!
Cons : Ends turn dark with use and will get scratched up over time but you're working against metal so that should be expected.
Other Thoughts : Burnishing foil leaves a silver cast on the ends of your fid. Take alcohol and a little soaking, then a little scrubbing and they clean up pretty good. They also clean up nicely in the silverware rack in the dishwasher.