Chalkboards that are worth a darn are hard to come by these days.
Real slate boards are great but rare in a big size. The green boards are just a special paint.
The ones University's use are often rather good.
Also chalk can easily be "patted" out of fabrics, whiteboard 'dust' ruins the cuffs on a white shirt. (yes the markers emit bloody fine 'dust' particles.
Chalkboard > Smartboard > Whiteboard.
Also don't forgot the epic chalkboard eraser battles.