The cat of course! But seriously, they sleep all day, and when they're not doing that they're busy eating, they play to their heart's content, plus they get petted whenever we get home from work, and all without stressing a muscle. Dogs on the other hand work hard for a living - they have to fetch, they have to beg when commanded to do so, many are gainfully employed by society (sight seeing, drug sniffing, hunting, etc.), and as if that weren't enough, those up north spend their entire lives doing back breaking labor pulling sleds.
Anyway, all jokes aside, it's commonly believed that the cat has more sensitive sight and hearing, but probably not better smell than the canine. They are certainly much better adapted for mobility (springing, jumping, climbing), have very flexible bodies which are capable of surviving falls from extreme heights, and make much better hunters since they have the added advantage of nighttime hunting (thanks to their superior sight, their whiskers and their very sharp sense of hearing) and stealth hunting (stalking, pouncing on prey). Their movements are undetectable, and the bottom of their paws are very sensitive to ground movements and tremors, which makes them capable of detecting prey several meters away. By night they require almost no light to see their prey clearly.
I prefer cats because they're very independent, very clean, they look after and take care for themselves, I don't have to walk them at 4 in the morning, and they don't constantly need your attention. During the course of a normal day, I take care of my business, and the cat takes care of his. We pass each other in the hallway but that's about it, since we each have our own affairs to tend to. At the end of the day we spend time together playing, snuggling, or just watching TV, and at night he sleeps next to me in bed. No wierd odors, no dirty paws, no wet tongue waking me in the morning, although he has been known to walk all over my head whenever I miss his breakfast.