I have no reason to trust a spray can. I have lots of experience which says to not trust a spray can.
Do they work in the cold?
Do they leak down if the valve is bumped once - like a powder fire extinguisher?
How would I know if half of the pressure is gone?
How many of the spray cans in your garage would you trust with your life?
How can I know if the nozzle is plugged up? This question has story. Went for a walk with my wife - who faithfully carries a bear spray daily for a four mile walk or eight mile bicycle ride - anyways, she hands the seasoning can to me to carry and after a while, I pull it out and look at it - still has the wax seal in the nozzle ... hey - they don't have a wax seal - this is ... clay - it must have fallen in a puddle sometime in the previous year or so - and so I spent a long time digging with my leatherman to clear it - wondering how many times she has been followed by critters. This is no joke - she sees more wolves and bears and three times, she has seen cougars. Once last week, she was within 90 yards of one - it came out on the road and stopped to watch her - not very tall but a tail about 30" she figured - as she turned her bike around and headed for home.
Anyways, this pepper spray versus lead spray is nonsense - they are each tools, but what spray can is as certain to work as a modern gun?
Put the spray can salesman in a cage with a hungry beast and give him a one year old spray can - and tell him that if his can doesn't work, it's okay - we will have another two year old spray can out here to cover him with.
And - I understand that pepper spray does not work so well on cats - apparently they have eye lids that are good at protection from spray. Grab your house cat and pull its eye lids open and you will see that there are three covers over the eyeball.
Pepper spray - phah