The only brown sugar I've tried so far was from WSP. I wasn't as impressed as I am with most of their scents, this one was not very strong in my opinion.
Sweetcakes has a luscious Brown Sugar fragrance. I adore it in scrubs. They also have a Brown Sugar and Spice which has a hint of green tea to it. Both work beautifully.
I tried WSP's and in my case it wasn't just that it wasn't strong after soaping, it wasn't brown sugar-y anymore, either. It took on sort of a "blah" nondescript smell to me.