Perhaps I should expound on my explanation, Coil.
The choice between the two standards would largely be based upon what force I am expecting my opponent to field.
If I am facing Devout, for example.
Almost all of the army of the Devout either a. Causes Fear, or b. is Steadfast, or both.
In this case, the Standard of Fright is virtually worthless, since models that are Steadfast, and Cause Fear, are immune to Fear. The Standards of Fortitude or Steadfastness are much more valuable in such a case.
If I am facing an army with generally low Leadership, the Standard of Fright becomes much more valuable, as many players generally underestimate the effects the Morale can truly have upon an army, if used skillfully.
The standard only causes Fear and doesn't protect against it.
Hmm...I'm not sure I necessarily agree with this, but hey...you're the boss.

I can definitely live with it.