What I learned is that, essentially, there is none: both are capsicum sprays meant to deter or disable whatever they're sprayed at/on. The big difference between them seems to be primarily the container - and more specifically, how it works. Personal defense pepper spray is generally fired in a stream or narrow spray for a relatively short distance; Bear spray goes out as more of a fog and appreciably farther (keep the bear farther away).
Interestingly, both products would seem to be capable of being used in the other situation - at least, theoretically (bear spray comes in a MUCH larger cannister to compensate).
So where am I going with all this?
One of the things I found during my research is that a lot of bear spray dealers will NOT sell to anyone in New York City, Washington (DC), and other locations that have laws prohibiting the ownership/carrying/use of "defensive" pepper spray (among other potential weapons - all an extension of anti-gun sentiments).
When I learned that little detail, I got off on a tangent of why... and ultimately ended up learning about Warren v. District of Columbia, and a few others. Basically, no less that the U.S. Supreme Court (and a multitude of similar judgements) have ruled that:
(the U.S. Supreme Court ruled that local law-enforcement had no duty to protect individuals, but only a general duty to enforce the laws.) South v. Maryland, 59 U.S. (How.) 396, 15 L.Ed.433The consensus is that this means that while the police and other law enforcement have a duty and obligation to protect the public in general, any failure on their part to do so does not make them liable in a court of law (i.e. you can't sue them for not protecting you INDIVIDUALLY).
So here we are in an "interesting" situation: if you get mugged, shot, killed, raped, or experience some other Bad Thing, you are not allowed to seek redress against the police - yet places like NYC, DC, and others are telling you that you can't have anything even remotely effective to protect yourself. Wait... what?
Is it me, or is there a pretty big disconnect there: I can't EXPECT protection by the police, according to the courts, but local government is telling me I can't have anything to defend MYSELF with?
Fuck that.
I'm carrying my bear spray everywhere, and if some shitbird tries to rob me, he's getting a face full of capsicum; if law enforcement has a problem with that, then I'm perfectly willing to let a jury decide whether the government has the right to tell me I have to be a victim or not - and, hopefully, throw out an unjust statute. As Dave Barry says, I am not making this up: juries can do that, even though the courts don't like to admit it.