Which Dress Should I Pick?

Oh my, what a dilemma! Well, actually it is. When I cleaned out my closet, I discovered that I doesn't own any thing that's suitable for a birthday party, nicer dinner and events like that. Of course, I got a lot of nice stuff, but when I really want to dress up in something that I wouldn't wear to work, I got nothing, I can wear everything to work. So the question is; which dress?

It's the same dress, in my two favorite colors: black and grey. The grey is 129,- and the black is 239,-. I like em' both, but I'm leaning towards the grey one, black is so standard. With a black blazer and studded pumps it will look amazing, but then again, the LBD is immortal.