Most people are naturally more skilled at one or the other, and there are a lucky few who do both equally well. Whether you have good attention to detail or whether you can see the big picture easily and clearly is generally part of your personality. But it can also be a learned skill, if you wish to develop it.
Really wish that some of the people I work with would develop it.
Just as we need to see with both of our eyes in order to capture all of the nuances of an image, we need to gather information from both "big picture" and "detail" perspectives in order to fully understand. Like a puzzle, you don't get the "whole picture" until you have all the pieces.
If you tend to be a "big picture" learner, you should be aware that you may miss important details when you read, take notes, and study. You may "jump to conclusions" in your eagerness to look for patterns and relationships. In a similar way, if you tend to focus on details, you may not recognize the relationships between ideas that are also critical to full understanding. If you "can't see the forest for the trees," you may find it difficult to understand where the information is heading.
The implication is that we should strive for a balance between these two styles of learning. We should seek ways to get information from the opposite "brain," by practicing ways to get all the information we need and/or by working with others who tend to be strong in the opposite style.