I like the second one. Good perspective and feeling of "being there". I agree with some of the other comments re light and shadow. Don't be afraid to have patches of pure black for shadow or pure white (i.e no pencil) for bright light, just like you would in an atmospheric Bryce render. Also, perhaps a little softer shading; try using a 2B or 3B pencils and moving in very small circles out and around a central point, lightening the pressure as you go. Hmm... pretty difficult to describe in words ;)