ok, I am going to be a bitch and tear these apart. i'm sure these get props on here, because most of the people posting here are coming from a graphics backgroung, and are easily mistified with poeple's ability to draw or shade.
first, you are shading too much, the lightest parts of the body would benefit from being left unshaded altogether, and the darkest parts should be darked. It's all a bit middle-gound really
Second, you are getting all caught up in "I'm drawing a sexy girl" and not paying enough attention to the whole body shape. The hand and arm on the "tattooed" one is completely wrong - crammed in small in order to keep it on the page. It gives a drawing a sense on depth if you allow the body to be "cut off" by the edge of the page - ie, it makes for better composition.
The hair on the one grabbing her tits is awful. it derves as much time and effort as here tits do, but you've just scribbled in a bunch on random lines. Her tits look like some melons shes carrying against a flat chest, you went so nuts shading them that they are too spherical, and here cleavage looks like she has been kicked in the sternum. And the ott abs you gave her look like a second boobs is about to sprout beneath the one she is holding.
No doubt these were drawn from photo's = cool I do that too. But if you ever want to be able to render the body properly, you will need two things:
Practice with more than airbrushed photos of plastic girls.
AND
Actual life drawing
If these things aren't for you, satrt looking at doing more stylised, cartoony characters
Don't take this personally, I do actually have some experience in this area.....I am trying to help