I am not a real expert on Danchong, but from what I can gather, how a tea seller calls their Danchong is almost entirely up to them. The names generally just denote different grades. This is, I think, more or less the same type of problem as with tieguanyin -- there are lots of names for it, but at the end of the day, taste is what matters.
Songzhong Danchong is generally the best. Prices can be way high. Feng Huang is usually a grade or two down, but there is, I think, no real system to how that's named. I've also seen lots of names for lots of different Danchong at some tea sellers. More often than not, they are named for what kind of taste they resemble. They taste similar, for the most part, but Songzhong is certainly better.
With something like Guihuaxiang (Osmanthus) though, they might have actually added flower to the tea, so what you're tasting may not be the actual tea itself. So, buyer beware there.