I personally use an Arcteryx alpha smock. I have taken a few tumbles in it and slid down some muddy banks with no adverse consequences. I will give you a couple of thoughts about what makes a good ultra running jacket.
The hood is the feature that makes or breaks any waterproof jacket for me. You should be able to rotate your head in any direction, without it impairing your vision. Try it on with the hood fully toggled up at your local running shop before you buy it.
Both the jackets you have mentioned are excellent choices on paper, but for my money personal compatibility is the key.
Arrangment of pockets is also important. Will you be able to conveniently acess them while you are moving and wearing a pack?
Weight should be less than 300 grams.
When you try the coat on, tighten the cuffs around your wrists. Can you reach upward to a point above your head without the cuff pulling back, or the jacket lifting over your midriff? If not then you might be able to find one with a better fit.
Edited: 26/01/2013 at 22:00