If you have discipline, it's very convenient. You can manage your cash flow and know when and how much exactly is coming in and out of your account, and if you have an unexpected $2000 expense (say, something went wrong with your car), you can pay it now and have a month to fetch the money for it from wherever you keep the money - since keeping all your money on the same checking account is both wasteful and risky. Also, can get you a cool 2% back on every transaction (over the years, it comes to a non-trivial sum). Some can even do 5%.

All that requires discipline and planning of course. If you don't trust yourself with being able to keep it up for years - get a debit.