I would go for the campy based on the simplicity of the cable setup and the general performance that it delivers regardless of circumstances. Another factor is serviceability. I know that on Campy if it breaks you can fix it by replacing the small part that broke not the component that it is housed in. Replacement costs are lower and a $400 chainring for "better shifting", I am sure that I will not notice the slightly "crisper" shifting on the front for the several dozen shifts per ride! Nuts.
Shimano performs very well but the underlying engineering is not user friendly. My bias is towards, reliability, serviceability and, durability. Shimano does not measure up.
Also aesthetically speaking I think that Shimano has left the reservation (I ride Dura-Ace by the way). The new groups are hard on the eyes (those cranks...well even their mother would admit that they are ugly).
I will be moving to Campy when my Dura-Ace wears out, this is after 20 years of running variations of Dura-Ace. Where will I go; Chorus. It is a version of record with heavier materials but equal performance and durability. Ultegra is not a version of Dura-Ace, it is a poor inbreed cousin.