When it comes to learning something new, depth beats breadth.
In both fields, players tend to get attached to fancy techniques and fail to recognize that subtle internalization and refinement is much more important than the quantity of what is learned …. It is rarely a mysterious technique that drives us to the top, but rather a profound mastery of what may well be a basic skill set. Depth beats breadth any day of the week, because it opens a channel for the intangible, unconscious, creative components of our hidden potential.
— The Art of Learning: An Inner Journey to Optimal Performance