That first girl in your example looks amazing to me. I'd pick her easily over the second girl.
Fitness is attractive, but so are curves. A combination of the two is best, but unfortunately many women with curves are also not that fit. But curves are always preferred over no curves and fitness is always preferred over unfit
Different men are attracted to different types of girls. Likewise, different girls are attracted to different types of men.
The most ironic thing is that people in general, seem to want what they don't have. My curvier friends want to be skinnier. My skinny friends want to be curvier. Girls with naturally curly hair use a straightener. Girls with naturally straight hair use a curler.
Both links are appealing to me. I see nothing out of the ordinary.
But when you say ultra thin, I immediately thought of girls within the threshold of the recent Angelina Jolie. The only people who drool over ultra thin girls are OTHER GIRLS. Yes, the glamor obsessed bitches in Hollywood are the ones who tout the ultra skinny divas, not men.
The interpretation of curvy varies. This can include girls with a lot of fat to girls who have smaller amounts of fat. Girls who are really thin are not healthy. It would be better to see how you define curvy. You should do this by citing examples or linking pictures.