I ordered both colors in different sizes (xs and xxs) - petite were no longer available, so can't compare there.

color: i liked the black better for these reasons:
1) color can be worn year-round, just add a nice jacket or cardigan, and ok for winter season.
2) ivory was kind of see-through

size: xxs fit me better, the xs was wider and bigger arm holes.

sadly, the xxs was the ivory, so i didn't keep either of them.

ref: 115 lbs, 30dd, 26.5 in wasit