The best thing about USAA is their customer service. I'm a big fan of technology and USAA does a tremendous job on getting new technology and tools in the hands of its customers, but the customer service is what sets USAA apart from the big banks and insurers.
I have accounts at many large financial institutions and it is very difficult to work with their outsourced customer service departments. But USAA leverages local talent who understand the American financial culture.
I think customer service is a strong competitive advantage for USAA.