Look at how penalties are applied via a credit union - for example late payments tend to have a longer period before they are assessed and the fee itself tends to be lower than the big bank cards. In the fine print you might find that mistakes on your part don't lead as quickly to penalties or higher rates as they do with the banks.
Credit unions are also more likely to offer people with damaged credit the chance to get a card.
Like any card that piece of plastic would have higher rates and other limits - like a lower credit limit. But it can still be very valuable for people trying to repair their credit. Another credit union boats if the willingness to go out of their way to accommodate members of a member's family. So if want a card and intend to have sons and daughters, or even mom and dad, get a card too, a credit union might be a good place to start your inquiries. But credit unions, especially the smaller ones, usually offer fewer perks than the big cards companies.