If it was my choice I'd go for the second one. Depends on your style of dress - you want something that suits your personality and also, MOST important, something that you are comfortable in.

On final thought - If you are spending loads of money, NEVER underestimate the power of the "LITTLE BLACK DRESS" - a classic shift-style black short sleeve or sleeveless dress. I was a bridesmaid about 10 years ago, and the bride made her bridesmaids wear a classic-cut "Jackie O" style black knee-length dress. The photos were stunning, and (until I put on weight 3 years ago) I ALWAYS had the perfect semi-formal/formal dress in my wardrobe!

I mention this because with the back dress, I got 7 years wear out of it wheras my Matric Farewell dress (like graduation) was SILVER and PURPLE and ruched all over (Hey guys, it WAS the '80s) - It cost me a fortune and I NEVER wore it again.