Bear spray is consistently found to be more effective. You sound like someone who really wants his pet answer to be the right one despite the facts against it.

“If you’re a hunter, why not carry bear spray?” says Smith [biologist at BYU], who co-authored the study with Stephen Herrero, professor emeritus at the University of Calgary in Canada. “If you want to be the most conscientious you can be, carry both. If I had to choose one or the other, I’d go with bear spray.”

Mark Matheny was another initial skeptic, but his own brush with near death made him a believer. In September 1992, the then 39-year-old Montana man and a friend were bow-hunting deer in the Gallatin National Forest when they stumbled upon a mother grizzly with cubs.

The sow took Matheny down, chomping on his head. Matheny thought it was the end—until his companion emptied a four-ounce can of bear spray into the face of the bruin, causing it to flee.

http://news.nationalgeographic.com/2015/09/150925-grizzly-bears-attacks-science-animals-bear-spray/

If bear spray works on grizzlies, wouldn't it work even better on less aggressive black bears?