The first dress is nice, and fits you well, but I agree with Louis, the cut might make it a bit formal.
However... the black one seems to have alot of possibility for versatility. Probably not your daily MOTG grocery store wear, but depending on what your life involves...
I see that black dress with dressy or casual boots, flats or heels, worn over straight leg or skinny jeans, put a jacket over it, or a cardi, or a long sweater coat, belt, no belt, scarf, leggings, come summer put on a cute silver belt and pewter sandals... the possibilities are endless. I bought a black sheath dress last May for my MIL's funeral, and I've just started to discover the possibilities myself.
My vote is keep the black. Not sure about the other...