Baby is much harder, and we had a landshark, large breed puppy who I wanted to give back in the first two weeks.
But I could leave her alone all night after the first couple of nights (she slept through from day 3) whereas it was 6 months before any of my babies slept through - and 3 years for one of them.
It's generally frowned upon to leave your baby at home alone while you go out to the shop whereas you can leave a puppy.
Puppy eats 3 times a day, baby 600 million.
3 years down the line I now have a lovely, chill, easygoing dog. My children are all monsters - except for other people. (I love them dearly but they are hard work.)