I'm actually partial to cats overall, but now (after having one for almost 12 years) can't imagine life without a dog! So in response to the folks saying your lifestyle isn't "compatible" with a dog, I just wanted to respond to a few points.
- Dogs don't need much "space" (in terms of actual living space), as long as their exercise needs are being met; those needs differ from dog to dog, but usually a 30-60min walk + potty breaks if you don't have outdoor space is sufficient. I've lived in a 600sf apartment without balcony/patio with my 50lb dog, and his behavior was no better or worse than when we lived in a 1200sf house with a yard.
- Once they're past the potty-training/puppy stage, most dogs can hold it just fine during a human's normal work day. I work 8-9 hour variable shifts, always have, and Rudy never has accidents. Generally speaking (health conditions excepted), 10-11 hours is about the maximum time you should ask them to hold it. But I honestly don't understand why people are saying "you need a mid-day dog walker," unless it's a puppy or dog with bladder issues. Mine has managed just fine without mid-shift walks for 12 years now!
- In terms of noise levels, honestly my cats make more noise than my dog. But again, this differs depending on the breed and individual personalities. If you want a dog who's quieter, avoid tiny yappers like Pomeranians, Shih Tzus, Chihuahuas, etc. They tend to be more reactive; as I've joked before, they'll bark if a cricket farts a block away.
Also, don't get a Beagle or hound dog, unless you want nasty notes from your neighbors. If you want a REALLY quiet dog, Basenjis actually "yodel" instead, and husky/northern types "woo woo" (which I personally find more pleasant).
- Finally, forget whatever you've been conditioned to believe about large vs small dogs, as most people think the opposite of what's actually true. Large dogs tend to be quieter, can hold their bladders longer, (often) have lower energy levels, and don't need gigantic yards or 2000sf homes to be happy. Believe it or not, something like a St. Bernard or Greyhound usually fares better than Chihuahuas and the like when it comes to apartment living. I'd also recommend adopting a young adult instead of a puppy, since they should already be potty trained and more capable of staying home alone.
Good luck with whatever you decide!! I can't decide myself, which is why I have 3 cats AND a dog.