NOthing is. If you had a massive gasoline line leak, you might have to evacuate for a much longer period.
That’s just engineering.
Unlikely, Ammonia’s profile is more dangerous on every measure.
Ammonia A - Compressed Gas; B1 - Flammable Gas; D1A - Very Toxic; E - Corrosive
Gasoline B2 - Flammable Liquid; D2A - Very Toxic