Hands down, Survivorman.
And a lot of that choice comes down to what's been mentioned already... the guy on Man vs Wild isn't out there alone. He's got crew with him all the time. Whereas, on Survivorman, yeah he's got crew close enough for rescue if he direly needs it. But they're not two feet behind him (helping) the whole time.
The last eopisode of Man vs Wild I watched was where he was out in the Glades. I found myself nit-picking that whole episode. He's showing how to make a bed that's raised so that he can get out of the water and away from gators. Then he says build a small fire at one end. And gee, how convenient, he's got flint rocks with him. How many people that have run aground and destroyed their boat in the glades are carrying flint rocks?? I'd venture a guess at hardly any of them.
The next morning, he's showing to create a makeshift filter to fill his canteen with water by using his shirt to strain the dirt and leaves. He throws his dirty sopping shirt up onto his raised bed. Camera cuts and 30 seconds later in the playback, he grabs a clean dry shirt from where he had thrown the yucky one.
Not that dude doesn't have some great skills, but there's just too much outside interference for Man vs Wild to be a true "survival show" to me.
But on Survivorman, he only gets what a 'normal' person would have if caught in a similar situation. Like the one where he was in the Arizona desert for example. Scenario is that he's out biking for the day, wrecks/gets a flat/whatever, and all he has is the bike and what was in his pack, which is typical of what a person out cycling would have: a multi tool, water, and some snacks. That's it. And he shows people how to actually survive if that were to happen. MUCH more entertaining and informative to me.
Just my $0.02