RE: bad engines
Fox engines are great engines, but many people have no patience and do not want to break in the engines first. Fox engines don't wear out fast like some engines do. But people seem to like that instant gratification that those pre-worn in more loose engines give them. They just tend to replace their engines a lot as they wear out on them.
Considering how some people just seem to be unlucky with glow engines, I don't think there is one that'll work with those people.
But usually once a person gets one brand of engine to work OK for them, they tend to stick with it, as they have good luck with it then.