Cats vs. Dogs

Dogs. I feel like they are more social, whereas cats are more independent. Dogs also have more interactions such as walks, adventures, learning tricks and obstacles etc. They do need more care, and (depending on traits) more exercise, but there are ways to mitigate this in game.

• Exercise: If you have a pool, dogs will autonomously go swimming. If they are swimming, they will need walking less often.
  
• Housebreaking: Once your dog is housebroken they will ask to go out by whining at the door. Adding a doggy door saves your sim having to let them in and out.
  
• Pet Poop: Can be used as fertiliser, or cleaned up with robot vacuums (might require an upgrade). Can be profitable with certain illnesses (gold poop and gold bars worth good money).