So I shot with them twice both league on Domesday and Thursday. I did not notice a large differences between the naturals and the silica. There is like Getagrip said a stickiness to them. I think its more of a tacky feeling. Not sure how I would describe the difference between sticky and tacky though. lol. I let a friend shoot with them, and she said it felt like she forgot to wash her hands after eating and threw darts.
I got the impression from the target website that the coating would protect the darts from ware also. Obviously its to early to tell if that is the case or not.
I also like the copperish color of the coating.
So to me its worth the extra $15 to get the silica over the naturals.