I like the lined version more for its clarity than its detail.
The lineless version might be improved by some shading. For example, the zipper head has lost its bottom side/edge when its lines were removed. Is it simpler? Yes. Is its shape readable? Not so much.
The lines before helped establish a boundary. With the boundary removed, the shape has merged with the rest of the zipper and even the knee. It takes an active effort on the viewer's part to separate these three elements. But if you darken that bottom edge of the zipper head, it will probably bring it out and give it more definition.
Here's an example of a bit of what I was talking about: [link] If it looks like something you want to try, I encourage you to go for it.
I was actually going to put darker-colored lines for overlapping areas, but wanted to see how pure lineless would look. I'm adding the dark lines later, but slightly unsure on just how much to do (I'll show you what I mean later).