Wow congrats on the size 6 wedding dress that is so great! You will look beautiful in whatever you pick... just go with the one that you feel the most beautiful and comfortable in :)

I love the first! It really shows your body. In the second one the highlight is the dress not your body. You need to wear the dress, don't let the dress wear you!!

Wow, you look great in both! I think the first is more classy/elegant, the second more sexy. I do agree that the second does steal the spotlight away from you a little (although if that is your personality, then on your big day when you are all dolled up, and glowy, I'm sure you will steal it back ;-). Both look fantastic on you, but I think the first complements your body and face better. I think whichever is more "you" is the better choice.
One tip I have from my/friends dress buying experiences is to try them both on again and don't "think" just "feel". By that I mean, which makes you feel happy, beautiful, and confident? Which one makes you "feel" like a bride? Which one makes you want to cry and scream "I'm getting married!" from the rooftops? If you have that feeling, then that is the dress you should buy.