If you want to hit your g-spot or better...for what?
The Diamond Spot, while having a g-spot curve, isn't very long. It'd be more of a hassle than anything else to attempt to hit your g-spot with that tiny toy. The Pretty Pearl has a bit of an odd scent, but it's easy to insert.
Based on the ratings, I would go with the pretty pearl, but from what I what I hear, you can't fail with the Lelo Ella even though it may be nearly double the price of both of these. It may be worth the extra. It's what's next on my list.