IMO, alot of people confuse tornado shelters with survival shelters/panic rooms. There is no need for large amounts of food and water supplies, beds, etc in a tornado shelter. If you desire peace of mind from potential tornados your goal should be to get a shelter that is as small as possible, as aerodynamic as possible, as strong as possible, and with as strong an anchoring system as possible (if above ground). If tornadoes are what you are considering, then time spent inside the shelter is only 15-20 minutes or less, especially if the door can be lifted straight off the hinges in the case of being blocked by debris. When people see my shelter their first response is, "damn how can you fit food and water in there?!". Tornado shelters shouldn't be built for that purpose. If you want a multi purpose shelter, then sure, go bigger. For me, I had a specific space in my garage, it's only me/wife/2 dogs, so this is perfect.
https://www.newdaytornadoshelters.com/It's 1/4" thicker than the similar Home Depot brands. It's padded and lighted, and also has a ton of additional features not found in the Home Depot ones. In the age of tv and radar technology, there is no need to immediately get into a storm shelter as soon as a Tornado Warning is issued. These days I get text messages from the Rockwall County Office of Emergency Management that has hyper localized information including intersection and direction of travel for any tornadoes. With this last outbreak we had one spotted about 3 miles North of us but it was moving Northeast so we didn't spend any time in the shelter. We just hang out close to it with the door open while watching and listening to tv, live streams, etc. In the event of a tornado that destroys our house, we'd only be in the shelter a few minutes.