Maybe I should have been a little more clear. Metal gear servos are always the best choice and I will never argue that point, but let me ask you this.

Why is it that almost every large plane has the most servos on the rudder and almost every manufacturer always recommends the highest torque servos be on the rudder?

I for one believe in overkill when it comes to torque. I will always use more servo than is required and always metal gear. A good example is the GP ultimate. That's a huge rudder, the minumum required is 130 ounce but I have 250 ounces

My point is all surfaces are equally important.