Which mortgage broker to trust?

[Ikhtiyar Uddin]

I am a first time home buyer with excellent credit and income. I am ready to close on a property. The broker I was working with for the last 8 months seemed as good as any so I initiated the process with him. He said the best he can do is 4.25% interest rate. Just for the heck of it, I checked with a couple of other brokers and got offered 3.75% rate with $8750 lenders credit. When I informed my current broker that i am getting better rates from other banks, he asked me to trust him and tried to warn me that not all the mortgage brokers are 100% truthful and often do bait and switch. But he said the best he can do is 3.875% interest rate and $3500 lender's credit. 

Since i have been working with him for the last 8 months, I sort of trust him. He has good feedback on Zillow. So I went with him.

Did I do the right thing? Is there a way to screen good mortgage brokers from not so good ones?