Well Rounded or Well Defined?

Which is better, being a well rounded man with a little taste for everything, or being a well defined man who has learned to excel in the narrow areas that he has chosen for himself?

I can not quite say. In my experience, oftentimes the only way around whatever your present difficulties are is to go looking in areas that are not a part of your life. Adding territory to your comfort zone, that is, becoming more well-rounded. On the other hand, time is quite limited, you cannot reach the summits in any aspect of life if you spend all your time exploring the foot of the mountain. Which suggests that there is reason to prefer being well defined.

Naturally, both of these have their charms, and there are balances that can be struck between the two. But I am not just being abstract here, there is a practical question to be answered here. When I choose my next book, should I stay within my common ground, or choose something out of the ordinary for myself?