What is the best cash-back rewards credit card? Bankrate.com aimed to find out in its 2010 Cash-Back Credit Card Study. We surveyed all cash-back rewards credit cards offered by the 10 largest U.S. issuers as well as several investment cards that offered a competitive reward ratio. Credit cards from Charles Schwab were originally included, but the company recently stopped accepting new applicants.

We examined 30 cards on 12 data points, including whether a card had an annual fee, an expiration date on points, a payout cap and reward tiers. For the cards that used points in the rewards formula, we computed a cash-back ratio to make comparison easy.

The results showed that while there was no clear winner for every type of card user, investment cards offered higher returns, and certain cards awarded larger payouts for big spenders and transactions in special purchase categories. Half the cards we surveyed provided a mere 1 percent return on purchases.

Cards with the highest returns

You could earn big with the TrueEarnings Card from Costco and American Express. This card pays out annually in the form of a rebate coupon redeemable at Costco for cash or merchandise, but offers 3 percent cash back on annual gasoline purchases up to $3,000, 3 percent on dining, 2 percent on travel and 1 percent on everything else.

Nine cards offered higher rebates for purchases in certain spending categories. For example, Chase Freedom awards 5 percent cash back for transactions in special categories that change quarterly, and 1 percent on all other purchases.

Best credit cards for big spenders

Seven credit cards offer tiered reward rates. For instance, the Capital One No Hassle Cash Rewards Credit Card for excellent credit gives you 3 percent cash back on gas and grocery purchases after spending $6,000 per year. Until you hit that threshold, you'd earn the standard 1 percent cash-back rate.

Blue Cash from American Express offers the biggest possible return. After $6,500 in spending, the rebate percentage for "everyday purchases" jumps to 5 percent from 1 percent, and the cash-back rate for all other purchases goes from 0.5 percent to 1.25 percent. You'd have to spend almost $1,100 a month to reach the higher cash-back rate mid-year.

Not all reward tiers go higher than the 1 percent baseline. With the Discover Motiva Card, you would start earning 1 percent cash back after $3,000 in total annual purchases, but until then you would make 0.25 percent back.