They do look very similar, their petioles are almost the same at young age, their leaves both have pigmentation...
The only (unreliable) way to guess what you actually have is to see the width of the pseudostem. Young DCs have thicker pstems than GN, whereas they have the same sized leaves (at young age). When the GNs get older, they form longer, more adult looking leaves much faster than DC.
At least that's what I've observed so far. Goof luck and good weather.
