What's the difference between snow blades & Skis?

I think the biggest difference in them is your stance when you are going down the hill. Because the snow blades are so short, you cannot lean as far forward as you would on skies or you will catch a tip and wipe out.
For many people, not having poles is a strange, out of control feeling when you are skiing. That unsteadiness would transfer over to snow blades.
As for advantages, I would consider their speed and size an advantage for many people. They don't go as fast as skis or snowboards, and also don't have long planks attached to your feet to get caught up in. You would be less likely to be injured. Plus, they are easier to get back up on if and when you wipe out.