First off, I am not storm shelter expert. But I do know containers. Secondly, let me say that containers are not the answer for everyone.
The bottom line is that you have to find the solution that works best for you. Of course you need to take into consideration your budget and local zoning as well. One website that asks a lot of good questions is TornadoProject.com. Check them out for more questions to ask yourself. Make sure you choose the best option for your needs, your area and your land as well. But above all, please stay safe during severe weather.