Chase Freeedom is a better cash back rewards card than Discover. I have both, they have the exact same quarterly 5% cash back programs except that the cap on DIscover is usually 5% back on up to $300 spent and Chase is 5% cash back on up to $1500.
I have both because rarely one will have promotions that the other will not have that will fit my purchases better at the time. For example, Discover sent me a special only for me promotion this year that if I spent $4500 on my CC over January, February, and March I would get an additional $225 in rewards. I had a few big things to buy so I just moved them off and I didn't pay a cent in interest and averaged about 8% total cash back on that deal.
Remember that if you do any shopping online with your rewards card to go into your account on their website and see if the retailer you are buying from is listed as an extra cash back reward dealer. You can get anywhere from 2-20% extra cash back at places like Best Buy, Bass Pro and Cabelas just by clicking a link in your account before you buy something that you were going to buy anyway.
Also, FWIW, my wife just got a Chase Freedom Visa pre-approved letter in the mail that she will get $300 in rewards just for making one purchase on a card if she signs up. We were looking for a rewards card for her anyway so we jumped on that.