The Predator design has its advantages, but as in anything else in life you'll find downsides as well. Not knowing all of the parameters of the actual testing it would be hard to comment specifically about it. The basic situation is that with their design they have larger window of where they will work well, but as a rule of thumb do not perform as well as the properly sized and tuned modular carburetor. Which is what Keith was trying to say. Most racers who used them have run better with a modular carburetor.
You're both correct, and incorrect when you talk about fear of change. Guys, and racers in general like to use what they are comfortable with, but if you showed up with something that looked strange and ran quicker and faster consistently with it they'd all look at it. It happens at all levels of racing, performance beats out unwillingness to change every time.