I had/used everything from blackboards to digital whiteboards. I still like blackboards better, but it's only going to last as long as digital displays improve.

Blackboards lasts forever. Whiteboards, especially the cheap ones, inevitably start to have stains that you cannot clean without some solvent.

Blackboards work with any chalk, essentially. You have to be careful about whiteboard markers, because many stink to oblivion (I get asthma out of them), and many others don't erase properly. One of the best markers I tried are the water-based made from Edding, but they're harder to clean, and you have to clean within a couple of hours in order to be able to clean at all. Chalk, on the other hand, lasts forever and can always be cleaned. If you want a perfect blackboard, just use a damp cloth.

There's this illusion that whiteboards are cleaner. Actually, they're not. Whiteboard "dry" markers work by depositing a fine powder on the surface. It's initially suspended in a liquid, and then sticks on the whiteboard "ideally" only due to electrostatic tension. Dry marker powder is often toxic, the suspension liquid is often toxic (especially when you breathe it), and the powder sticks fucng everywhere. If you're careful when erasing, a blackboard can be kept very clean. I have one in the kitchen.

The markers are expensive. Especially when you want the good, water-based ones. I often have to order those. Chalk is inexpensive, I can buy it anywhere.

Why the hell are we using whiteboards??

I built several whiteboards myself. They suck. The best approach to a whiteboard is buying a piece of glass the size you want, and gluing a piece of white adhesive plastic on the back side. Dry marker on the glass always cleans. You might get stains if you leave the marker for days, but they come off easily, with just water.

Now what.. digital whiteboards. It's a love-hate relationship. They're completely clean, which is what I like about them, but there are many downsides too. You need power, which means that you need to switch the screen off. A white/blackboard on the other hand shows you stuff all the time.

The screen is large, but the pixels are too large. The DPI, at close distance, is ridiculous. They're also too bright when seen at close distance. There's glare. The "pens" suck. But if you did the same with some e-ink technology, I would switch to digital whiteboards instantly, as it would solve all these problems at once. It looks like a dream application where the price of the display wouldn't matter much (ardesia costs a fortune nowdays anyway).

I had to use at some point an Epson projector which had some whiteboard capability on it. The pen had an infrared sensor/reflector on top, which meant that you had to hold the pen without making a shadow between the projector and the pen. Who's the idiot that thought this would work??