I'm an Evo and like both, to be honest. But, if I was forced to choose between the two, I would have to go dog. I love cats and grew up with a couple of them, only to have both of them runoff.
The greatest reason I do not have a cat as of now is because of the vast amount of birds that live around my house. Swooping through backyard to backyard, looking for food, nesting in and around trees in my yard, this cat could possibly kill many of them.
I recall watching an Ultimate Guide edition on the Science Channel about cats. The house cat was the most successful predator of all the cats. They kill, if I remember correctly, between 3-5 billion birds annually in the U.S. alone.
To my liking, my dog is rather indifferent to birds. However, I'm sure the simple solution would be to keep my cat indoors more often.
Nothing in particular against cats; I think they are great companions and interesting pets, but dogs are hands-down a greater pet. Perhaps my ignorance speaks for itself, but I believe the credentials for dogs is incomparable.
Dogs assist with the seeing and hearing impaired, detect drugs and explosives, guard property and people, herd livestock, hunt and retrieve game, assist with law enforcement, assist with rescue teams, and are "trained to provide comfort and affection to hospitalized and institutionalized patients".
Dogs even have the ability to detect cancer from our breath. http://news.nationalgeographic.com/news/2006/01/0112_060112_dog_cancer.html
Also, I saw a PBS special on dogs in which case a diabetic child had a dog that could detect when the childs blood sugar levels were low. The dog would leap on the parents bed, wake them, and the parents would administer the insulin. It was truly remarkable to witness this.