Babies. No doubt whatsoever.
My daughter had colic for the first 2 1/2 months of her life. She screamed 24 hours a day, 7 days a week, taking what seemed to be 5 minute catnaps on my shoulder while I walked her. We tried every colic remedy in the book: Car rides, car seat on the dryer, vacuuming with her in arms, rocking... and many, many more. Suddenly, one night, she slept 7 hours straight. I thought she was dead, but didn't want to touch her just in case she WASN'T - it sounds awful, but I held a mirror up to her face to see if she was still breathing.
Babies are not generally even ambulatory for the first six or seven months. They must be carried everywhere. And they weigh more than puppies. I have a permanent crease on my left arm from baby butts. I learned how to hold the baby and write a check at the same time without juggling either one.
Babies before six months are sometimes pretty floppy. If you don't hold them just right, they flop around and are easy to drop. No, I never did, but came close a few times. Even after that, occasionally, they will stiffen up and attempt to FLING themselves out of your arms.
It is far easier to dog-proof a house than to baby-proof it. Let's face it, dogs aren't about to stick their slimy fingers into wall sockets, or pull the sharp knife drawer down on themselves. Or, yank the new kitchen television off the counter and onto themselves just after you'd finished getting it out of the box and set up. Yeah, that happened. The kid was fine, the TV fried.
Dogs are far easier to contain with child gates than children. Especially after the children become ambulatory. Kids learn to climb over those suckers at the drop of a hat.
You can keep a puppy in a crate, where it can't gnaw on things, pee all over the place, crap on the floor, or anything else of an unsavory nature. Try sticking a kid in a crate and see how fast someone calls Protective Services.
People don't object to seeing puppies and dogs on leashes, but if you have an escape-artist kid and need to corral them in public, see how many people make horrified faces at you if you have your kid on a rope.
Those are just a few that are permanently etched in my memory.
~~Wiccan~~