Both are pretty but the turqoise one draws your eye to the top half of the dress. Great if you want to draw attention away from wide hips or tummy but not so good if you don't want to highlight your boobs.
I'd go for the red and black one myself.
I don't know if anyone else agrees but I think turqoise tends to look better on really sunny days. I always think of it as an "On holiday" colour.