Gorillas are amazing. I wouldn't feel threatened by one at all in those situations as, even though one would absolutely fuck you up if it took a disliking to you, they don't seem to really attack much unless threatened. If you stare at them, for example(as it says in the video about avoiding eye contact), it would likely aggravate them, although I wouldn't like someone staring at me either if I'm honest!
As for chimps, they seem much more unpredictable, so I wouldn't want to go near one of those bastards.