Best W.S. ballast size for N scale ?

I used medium years ago and it didn't work at all. I have fine ballast now, and although I haven't used it, I can tell it will work out much better. It is still too large scale-wise, but it LOOKS right, which is what really matters.
 
Thanks to all the nice people who took some of their time to reply.
I had some medium type left from a HO diorama, and following your opinions I purchased some fine type
I did some ballast testing and I agree that the "fine" ballast type looks better.
Good idea TruckLover to use the medium type for hills.