Personally, the right one looks better to me. It's a difficult shape to convey though, isn't it? I thought I'd share this since I looked up "greyscale lemon" on image search. There are a lot of different images, but the key I'd think is trying to add a bit more visual distinctiveness to it. In this, for example, you can see the interior of the fruit. In some other examples, the pitting is done only in small amounts, or at the edges of the shape, which might make them stand out more (vs the entire surface being pitted).

I worked on this a little bit more. How does this look?

Of the original 2 the one on the right was def. better.  This latter one is better yet though since it shows some depth.  I find myself imagining it darker (a bit of shadow) on the far side (left) opposite the white dots though.

I kind of liked it lighter because I feel it conveys the idea of a bright yellow color better.  Just my opinion.  The revised pic looks good also.  Either would work.

Lighter. I say put the light gradient on the top left, and a dark gradient on the bottom right.

Oh, and you could divide the lemon into four quads.  They can all then be the same image flipped and rotated with pallet swaps.