IMHO having a TX with the option of dual rates and not using them is like buying a car with A/C and not using it.

Set them up and if the plane is too twitchy on that first flight switch to low rates and get more comfortable.

HOWEVER I do agree with the people who say that if you are careless enough to fly with the wrong rate selected then it can be a problem. Thats why you do a preflight check.