It seems a little formal for a wedding mostly because it's long; it strikes me as more of a Mother of bride or groom dress- not that it's matronly, just a bit dressy for a " regular wedding guest", IMO
I agree with the others that say the dress on the right is more youthful
As far as which color to chose, it does depend on which colors look best on you. What is your hair color, your skin tone, your eye color for instance.
I wouldn't wear it to a wedding, if it was short then maybe.