When I was in Uni my Animal Behaviour prof worked around grizz a lot in Haida Gwaii. Like very, very, close; sampling salmon carcass and scat etc. while the bears are feeding in the same reach. He felt that the bear spray's main value is that it gives the human enough confidence to be calm around the bears. After years of working with the bears, and bringing multiple grad students up with him, the only times the bears acted aggressively was when particular grad students would be fearful - the bears would chase him/her right the eff out of there. Same student carrying bear spray felt comfortable (possibly not rightly so buuut..) and the bears left her alone.
I bet that things are different with habituated/starving/hungry/cub protecting bears. "His" populations were quite wild and very well-fed. The same prof also felt that a grizz that wants to eat you will eat you, bear spray (and most firearms) won't stop him before he's torn you up.
My only suggestion about carrying is to look closely at the bottle you're buying and make sure that it's design is compatible with your use. I can't see any of the bottles I've owned opening by mistake, but it happens, probably more with some designs than others.