I think it's all about proportion and how toned you are, as well as your height, your natural shape, etc. People look best when they're healthy and happy with themselves, whatever that size may be.
I personally think a size 14 woman could look absolutely beautiful in her body, just as a size 8 woman could. I think it's difficult to have a curvy but slim look though. Most people who are a size 14 will have some kind of tummy on them. I'm not saying they're fat necessarily. We all have our good and bad points, if you have the boobs, hips and curves, you'll probably have some kind of tummy, whereas if you could grate cheese on your abs you probably won't have the soft curves a lot of women aspire to.