Both. Some are fast and skittish, and if they launch, even a short fall would be fatal. Description of the bite is similar to a wasp sting; only dangerous if anaphylaxis.
Their bite is much worse than a wasp sting. Unlikely to cause death or serious injury in an adult with no allergies, but the pain can be excruciating and last for many hours, and lesser symptoms for days. We usually do not prescribe muscle relaxers or opiates for a wasp sting.