For the sweetest deals on certificates of deposit, consumers are typically steered to credit unions. But the competition is getting stiffer for the cooperatives.

According to 1,300 banks and credit unions tracked by Market Rates Insight, the premium paid on short-term CDs increased from 66.3% in January to 100.4% in September, an increase of 34.1%. Short-term CDs are defined as those with a one year or less term. Meanwhile, the premium paid on long-term CDs decreased from 48.4% in January to 46.3% in September, which only amounted to a decrease of 2.1%.

"It's a mixture of uncertainty and the job market," said Dan Geller executive vice president of Market Rates Insight, a San Anselmo, Calif. firm that tracks rates loans, fees and rates. "The bottom line is people prefer to make short-term commitments in case they need the funds."

Still, some CUs are not giving up their top CD spots easily. According to bankrate.com, as of Oct. 15, the nation's highest yielding one-year and six-month CDs was offered by Wings Financial Federal Credit Union at 2.75% and 2.35%, respectively. The rates were well above the same highest yielding products at banks. Ally Bank topped the list with a 2.03% rate on its one-year CD and a 1.64% rate on its six-month CD.