I had to put my lovely baby-dog down last August, aged 14.
I got her a couple of years before my first nephew arrived and I used to joke about how much easier a dog was than a baby -- three days to toilet train and able to be tied up outside the shops or left in the car (for short periods, with the windows down). I filled up her food and water bowls when they were empty. In return she gave so much love and shared her absolute joy at being alive.
I still miss her so much. We have a new dog now, who is a sweet thing but not as adorable as my old pal.
I am getting a bit worried about my reaction to the baby, actually, because it's going to be so much more work than a dog.
I don't think anyone should get a dog for "practice". Having a special dog friend is only rewarding if you like the way dogs operate.