I own So Ceylon but don't have Brunette. But, based on the swatches and pictures I've seen, So Ceylon seems to be more versatile in terms of color and more wearable for your NC15 skintone (I've heard Brunette is very pigmented). Brunette seems to have stronger coppery red tones, whereas So Ceylon is a gold bronzy-brown with a hint of rose.
I am absolutely fair and own both of these. I love So Ceylon; it's a perfect slightly rosy bronze colour that doesn't turn orange on me and doesn't make me look dirty. It's a lot easier to throw on, too. Brunette is much more reddish. Beautiful, but more work.
so ceylon it is!
thanks everyone. i know i own redhead and its wayyyy pigmented. id probably look like i rolled in mud if i had a boo boo with brunette.