Which dress?

I need a dress to go to a wedding that:

1.)  Won't wrinkle in my suitcase
2.)  Won't wardrobe malfunction at the most aggressive dance party since 2007
3.)  Will be prepared for a limbo competition
4.)  Is a good addition to my lineup

So I love this one....

...because it is elegant and drapey (most likely flattering) and the strap will keep it on me, but do not love that is is another almost-black dress to add to my boring attire.

But I love this one....

... mostly because it is purple, and I have no purple, and I want some badly. 

I have two votes for the first and I'm still leaning toward the second.  Why doesn't the first one come in purple?  Do I just order them both and decide based on fit?

Help.