Back in the old days of snomobiling, Champion got a pretty bad reputation...they didn't have as many heat ranges available, or their quality control wasn't all that great. Keep in mind that the mid-'60's to mid-'70's two-strokes were plug eaters no matter what went into 'em. Just about everybody experimented with different plugs in their sleds, and developed favorites...NGK, Bosch, BG, Beru, Nippondenso, even AC, Autolite and Champion got tried if they had a heat range close to what was "supposed" to be required.
NGK and Bosch had the widest approval rating for fouling resistance.
I think Champion still has a lot of holes in its line-up for oddball applications. But for plain-vanilla uses, like my Ford pickup, they do fine. I also use them in most of my small-engine stuff because they are easily available and cheap. There isn't any reason for it, but retailers capitalize on NGK's reputation in my area by overcharging. The plug for most of my chain saws in Champion is about $1.50...why does the same store want $3.25 for an NGK?