I also recommend Commercial bank.

Its online service is superb it saves you from going to the branch. refer to this thread http://www.qatarliving.com/discussion/banking-in-qatar-09jun2006 customer service in CBQ is "relatively" better than other banks. Interest rate varies by bank and by service (vehicle loan, personal loan..etc).

Interest on Vehicle loans starts from 4% to 4.5% max.