Hmmm...interesting question. I only have one child, whose father was very much a bad and very compromised decision/choice on my part (abusive, neglectful, mean, just wrong in every way) who died (cancer) when DC was very young - still a toddler. I was then lucky enough to meet DH, who adopted DC after we married, and we've had an absolutely wonderful life.
So, yes, had I known EXACTLY how it would pan out, I would make the same decision again, despite the difficult years. But if I could go back and counsel my younger self, I would tell her to run, run like the wind! But then, I would not have had the lovely family I have today. Some shit, it seems, is worth eating. But I know that fate dealt me a very specific hand, and I couldn't really advise my course of action to anyone else.
DH and I did discuss another child when we married, but rapidly realised that we were happy as a three - it wasn't more work/expense/worry than we could manage, we could provide very well for one child with plenty to go around.
But even if I had been a single parent, and hadn't met DH, my life as a parent was much richer and happier, had purpose and pleasure that it hadn't before. I am glad I didn't have to contend with divorcing and co-parenting with a very difficult person though. I can't imagine that would have been easy.