I lean herbalism with skinning for most of my alts where other characters have the crafting professions.
Mining requires staying closer to the edges of a zone (if mountains or cliff-like) or along rocky terrain, as well as going deep into caves. Some zones seem barren of ore (Teldrassil, for example). Mining has a small chance of showing you a node as a yellow dot, only to find it is under the world if the terrain shift was too much in the area.
Herbalism is generally more out in the open, anywhere in the zone. (Some herbs are also along rocky terrain and the edges, but others are at the base of trees. You kind of learn where to look for each.) Herbalism has a terrible habit of making the plants look a lot like the groundcover. I was having a hell of a time seeing Sungrass in Feralas yesterday.
So pros and cons for both, but my experience has been that skinning requires me to be killing many beasts, and I run across more beast while doing herbalism, where mining I tend to follow the perimeter and not fight beasts as much.