Everyone learns better with a teacher because no matter how you think you learn best, getting feedback from someone who actually knows what they are talking about is required.
On personal & spiritual development it's very useful.
Often the process of formulating the question by writing it down or talking about leads me to understand the problem and either know where to find the answer or often know the answer. On theoretical matters I hardly ever had a question that wasn't answered properly by someone online or in a book.