The really nice thing about using hexes instead of octagons is you can line them up into rows easier. You keep them in half until you lay them out. I'll see if I can find a thread we had here before where I really grasped the concept!
With octagons you have to set in, or put triangles into the corners which can be a design element.
edit: it wasn't the thread I was thinking of, this older one has some great pictures, diagrams, and hints!
What am I missing (or am I really that dumb)?