The key here is integrity. Ray is a shrewd businessman but this isn't to be sneered at. He's built a good living out of his hobby and managed to retain his credibility and integrity in doing so. He's never (to my knowledge) claimed to be anything other than an enthusiast of bushcraft, primitive peoples, and nature in general. When you watch his shows the impression is that of someone who has done his research. His series on early British explorers was exemplary.Discovery make and script the programmes. Not Grylls. He is just paid to present and do what they tell him to do. The Discovery Channel has a history of turning out sensationalist rubbish dressed up as documentaries. Most people on the thread aren't Grylls fanboys, they are just trying to say "seperate the programme from the man". At the other end of the scale you have Ray Mears (yes, I'm a fanboy here). But Ray is a ruthless and coy businessman who has nearly always been in control of his programming from the early Extreme Survival series. I like him personally too, but I could never work for him. He is much more aware of how he should come across on TV and his own future and what it entails to secure that. Grylls wears his soul and heart on his sleeve and is naive in those aspects. Work for Ray and you'd have a strict and controlled working life. Work for Grylls and you'd have fun and a good mate as your boss. The company would probably not last long, but your friendship would.
I'm a fan of the same things. I know Edward Grylls is presenting a flashier, different kind of image and his shows reflect that. They are not to my taste because I'm a bushcraft enthusiast but there is a place for every kind of presentation. But the exposure of his shortcut methods (hotels; fake lava bridges etc) and his willingness to participate in stunts suggest a man who places style over substance and I've never found that attractive.
Finally, a word about working for the respective men: I posted on this site about a courier friend of mine dropping some airline tickets off to Ray's house last year. It was mentioned before his arrival that I was a fan of his work. So Ray kindly and without prompting signed a hardback edition of one of his books for me to keep. This doesn't necessarily prove he is good to work for but it does suggest a man with a good heart. Someone else I know was working on one of Grylls' shows as an assistant producer. He told me that swearing was banned on set because of his apparently Christian views and anyone caught doing so was asked to leave. A bit harsh considering the rough and ready world of TV production and ex-soldiers. This story is hearsay; I wasn't there to verify it so take it as you will, but it does make me ponder.