Pepper spray can be very effective but people can often fight through it depending on the person and their training. There are also a very small amount of people who are immune to the effects. while a stun gun should stop someone dead in their tracks for a limited amount of time depending on where contact is made and how complete the contact is toy would need to be very close given whats able to be carried for self defense most likely. Both can be effective. The pepper spray may be the better option to utilize while creating distance from the threat.