What kind of lender is "best?"
If you talk to a loan officer, he (or she) will probably say the lender they work for is "the best" and give you a list of reasons why. If you meet the same loan officer years later and he works for a different kind of lender, he will give you a list of reasons why that type of lender is better.
Realtors have differing opinions and, as a group, their opinions have changed over time. In the past, most would often recommend portfolio lenders - because they almost always closed the deal. As time passed, mortgage bankers and mortgage brokers became more important, and agents switched along with the changing times.
Most often a Realtor will direct you to a specific loan officer who has demonstrated a track record of service and reliability -- or a loan officer who works for a lender affiliated with their real estate office.
It is often more important to choose a good loan officer, not the institution. Loan officers have two jobs. One is to be your advocate in getting the loan approved. The other is to deliver quality loans. You want someone who has proven dependable and ethical in the past -- someone you can trust.
As for lending institutions, each type of lender has strengths and weaknesses. Quality within each branch or office can vary, depending on the loan officer, the support staff, and a variety of other factors.