So for me, the thing that's maybe attracting you to the coat is the colour - navy and orange are a fab combination. But the coat (fast or otherwise creds aside) is a bit of an edgy cut, whereas the dress is quite classic. I think the coat will drown the dress. That said, a wrap or whatever is so dating and part of my mindful buying thing is to always buy things you'll wear again and again. If you're not a wrap/shrug/whatever type person, you're basically buying one thing for one occasion that won't get worn again.
So. There are loads of tweedy double breasted blazers around which I think you'll get loads of wear out of. Or even a cropped bomber. Think of it as just a piece of outerwear, it doesn't need to 'match' that much but essentially just cover you a little bit while you're travelling. Whip it off in the service and no-one will even see it at the reception.