Should you paint on wood or on a canvas?

What's better to paint on? Wood or canvas? How durable is each of these supports? The choice is important in creating good quality work. Here’s my choice and why.

Making large-size paintings can become costly when using expensive paint, especially when creating a lot of texture. Why are some paints expensive and others much cheaper? How to choose? It all depends on what you're trying to achieve.

Paint is dry. I'm going for another layer. 

Third and fourth layers.