A new survey has found that 56% of consumers prefer cash back on their credit cards, while 23% said they favored air miles. About 12% preferred points and only 9% selected automatic rebates or discounts as their favorite rewards. The results from cardtrak.com are based on an online poll of 1,000 consumers completed last week. Nearly all general purpose credit cards offer some type of reward either at the network level or the issuer level. According to CardData the number of reward credit cards in the U.S. has grown from 290 million in 2002 to 490 million in 2006.