It's completely subjective. Both suits me but I have a small preference for the frosted optic.
It will be a little complicated to explain it in english as it isn't my main language but with the frosted optic, the center of the beam is still lightly more intense that the spill, so for short distance lightning, you have a more even light. At 10 meters, you have the same intensity than 1 meter. With the mule, you d'ont have that.
At very short distance (less than 2 meters), it not visible, but at short distance (8-12 meters) I find the frosted optic more even than the mule.
Hope it's understandable.
You have a great light. A fivemega surefire and a Tana drop-in is a amazing combo.