Lots of "campfire" conversations about this issue, which typically boils down to "use the proper tool" for the job. I have not run into anyone carrying bee spray (outside of trail maintainers) nor has anyone I have had conversation with advocated it.
Though manufacturers vary, pepper spray sold as personal protection devices has approximately 1-million SHUs (Scoville Heat Units that indicates the amount of capsaicin or "heat" potency in peppers). The delivery system is a directed single stream from arms length up to 12 feet that and is capable of delivering multiple "shots" of spray as needed. It can be carried in a holster or pocket, making it easy to reach if needed. There are approximately 10 to 15-seconds of spray in these cans (varies with size) allowing multiple "shots" against assailants. Disadvantage to this spray used on bears is how close the bear has to be before the spray can be effectively deployed as a stream.
Bear spray has approximately 3-million SHUs, making around 3-times more potent than pepper spray. As it relates to bears, the potency gets their attention pretty fast and will typically stop them. The delivery system is highly pressurize to release a cloud of spray toward the bear from 20 to 50 feet away (depending on wind direction) that the bear runs into as opposed to a single stream of 10 or so feet aimed at the nose of a charging bear . There are approximately 8-seconds of spray in most cans (varies with size) allowing a few discharges of 2 - 3 second each. The disadvantage to this spray is wind direction and wind drift back to the user that will quickly incapacitate them.
There are potential legal issues that can be involved with the use of either pepper or bear spray on humans, if carrying either (or both) you should understand the legal use parameters prior to use.