IMHO propane is superior, because I can store my supply on-site.
When you hook your generator up to the natural gas supply you are dependent on someone else to keep the gas flowing in that pipe.
Sure enough, if the natural gas supply keeps up it will last longer, but I already own the propane I have on site.
Well yeah you are not dependent on a gas company that’s true but if you are in a community that uses NG and it becomes unavailable at the same the power is out I’d say wherever you are is in crises. Comfort and spoiled food may not be your biggest problems.