I've experimented with both the fence brush and the lobby brush. Personally, I find that the lobby brush does the job better.
The fence brush is just that bit too dense for my liking and the bristles bunch up to form a wedge in tight areas. I find that this wedge of bristles stops me getting into the recesses of the brackets and right up behind the gutter.
The lobby brush, on the other hand, does absolutely everything that I want it to do.
I can't understand for the life of me why people use regular brushes when lobby brushes are a gazillion times better and quicker, not to mention lighter.