The only way to decide is to make a pros and cons list and compare, I suppose. That's how big decisions are made, right? So here goes:
Pro - a dog will probably want to snuggle you forever.
Con - dogs can stink so bad that you wouldn't want it to.
Pro - you have to walk it, so there are health benefits.
Con - you have to walk it, or it craps on your floor.
Pro - dogs are very loyal.
Con - it will crap on the ground forever. You will never get to stop stooping and scooping.
Pro - it will never pull teenage moody bullshit on you.
Con - it doesn't eventually get a job and take care of itself.
Con - they need a lot of room to run around.
Con - in general, they seem to lack respect for furniture.
Con - did I already mention they smell?
Con - they shed.
Pro - baby cuddles and snuggles are the absolute best.
Con - it breaks your heart when they start refusing to snuggle.
Pro - babies smell SO good.
Con - except when they don't.
Pro - they eventually become self sufficient.
Con - when they become more self sufficient, they think they know everything.
Pro - they eventually move out.
Con - they eventually move out, and may not visit you as much as you like.
Pro - if you're nice to them, they may send you on a cruise at some point.
Con - I'm scared of cruise ships. I should never have watched Titanic.
Pro - I would be less of a burden to my current children when I'm old and they're fighting about who has to visit mum this time.
Con - I would have less to give each of them.
Con - we don't have room for another baby.
Con - I was just starting to get to sleep through the night.
Con - it's probably a sign of mental instability to even be considering having another baby.
Con - we're almost through the diaper years. A new baby would mean starting again.
You know, I think I'll look into getting a fish. A nice, cuddly, stuffed fish.