How do you choose between 7 & 13?
The choice of which bankruptcy to file is based on your financial problems. Everybody has different issues that will determine which type of bankruptcy is appropriate. If you have limited assets and income and lots of credit card debt then a chapter 7 may be appropriate. If you own a small business, then it is likely that you would want to consider a chapter 13.
If you are considering filing for bankruptcy, I suggest consulting with an experienced bankruptcy attorney.