That is the 64 million dollar question, Everybody uses what is there own personal preference for whatever reason they have, I like Comp Cams myself and some people don't,Sometimes the best way to go is by checking the grind of a given manafacturer and seeing if it meets your needs, Also some companys do more public relations and advertising than others HTH
The best way to decide on a cam brand is to talk to the engine builder. Preferably one with experience building the type of performance engine you are using, SBF,BBF, FE
or brands C,M,or whatever. The guys with alot of experience can give you ideas. You can also talk to exp. racers and see what they win with. Keep in mind most of the racers use "custom" grinds, not the cams we run from off the shelf. Everybody still has a preference, just like the Chevro/Ford thing! Most all are good some better. I like the smaller manufacturer, they make time for you and seem to be interested in your engine.
I have had good luck with Engle and Comp. I have visited the Comp Cams shop in Memphis and liked the people. I guess you just have to ask around and try some cams! This is long winded,but you should be able to get the idea.
In all my ancient 47 years I've run quite a few different brands of cams. Right now running a Crane. Have run Ultra dyne, Crower, Cam dymanics, Comp cams, and a couple that I can't even remember.
I don't go so much for who's running what, but by calling the companies/tech lines and getting their suggestions/recommendations for whatever motor combo I"m putting together. You can learn alot about cams and the companies that make them by just doing that. My .002