First and foremost, improving your credit is the best option for getting loans. You are more likely to be able to get larger sums of cash if your credit rating is better. Getting cash can be much easier than dealing with banks and checks or money orders. With cash, the money is in your hand and you can pay for bills or buy something immediately. There is no secondary credit check with this kind of payment and you just have to worry about paying back the cash loan.
A cash loan with bad credit usually requires you to put down something for collateral, as that is the only way that there can be any guarantee that you will pay back the money you borrowed. Cash loans usually are more limited in the amount you can get and are not meant to be used to pay for larger purchases, such as homes. They are to be used more in emergency situations. For example, if you had to get your car fixed quickly, or pay rent that you couldn't come up with, a cash loan with bad credit might be an option. You will have to sign a contract and be liable for paying it back. There can be heavy consequences for late payment.
Cash can also be too easy to spend. This has its positives and negatives, meaning that it is easy to pay your emergency bills, but that it can lead to more frivolous spending on things that you don't need, furthering your debt and requiring more loans. Cash loans should be for emergencies, not extra spending money.