IMHO, JMHO I would use ONLY "Airline crates" period. You want them to be SAFE from flying debris etc. Just because you are in a building deemed to be safe during a tornado doesn't guarantee that nothing will happen to your or your pets from falling or flying debris.
I want my dogs to be in something safe to keep them from harm. Soft crates or carry bags that are 'convenient for the owner' is NOT what is going to keep them from being injured.
I have had to evacuate in a CG to a safe building with 4 of them. Using Airline crates also allow respect for others. You can stack the crates on top of each other allowing more room for others. AND a dog in a crate with his favorite bed is less likely to freak and/or injure themselves.
And if you get separated from them they are still safely contained.
Last month remodeling a winter home we had a part of the old ceiling which was made of concrete, not drywall, come crashing down RIGHT ON TOP of the dogs!:E
They were all in airline crates and were not harmed. Not even one dent on the crates. Thank GOD. :C
And BTW: Do NOT buy the cheap knock offs that most of the stores have. Buy Vari KENNEL brand airline crates.