We use all stranded at our shop, except to wrap the ground screws in the boxes. Stranded is easier to pull, easier to feed, and the wire doesn't get nicked going in the pipe like solid sometimes does. The price difference isn't too much and the labor savings makes up the difference anyways.
Although, there have been a few times when I wished I had solid wire when I was pushing shorter runs box to box. I just went to the truck, got out the fishtape, and tied them on. Would be nice to have the best of both worlds though.
