What are your brother's responsibilties and priorities? I wouldn't live on either one of the coasts without a 7-figure income. I'd choose OKC. Good private schools, cheap housing and low low cost of living. A million dollar house in OKC is 7,000 to 10,000 square feet. A million dollar house on either of the coasts is going to be either a crap hole or a hell of commute to work.
Sacremento - visited there and enjoyed it. Very similiar to Austin: cap city, and universities. But when it comes to residency, make a choice as to which will give you the best experience in your field. Just because you will be a resident there doesn't mean you'll 1) get to experience everything about the city and 2) doesn't mean you'll be living there forever. What is your speciality which bounds you to these options at the moment?