Your choice doesn't necessarily have to have anything to do with food, unless that food somehow affects your opinion of the sexiness.

Giada is the sexiest by far imo. Although i'd still hit Nigella.

Hard choice, i think im gonna go Nigella.

I will one day make Giada my wife.

Giada makes the same things over and over again (or a small variation of something)

But most people only watch her for her looks, so they wouldn't notice what she is cooking.

Did it ever occur to you that you might be watching a re-run?

Here are over 100 documented recipes: http://www.foodnetwork.com/giada-de-laurentiis/recipes/index.html