Oh god, I'll say what I always say on these threads.
People make stupid comments whatever you have:
One: lonely only, won't learn to share, when are you having another
Two of same sex: are you going to try for a boy/girl? Oh [opposite gender parent] you are totally outnumbered now. Additional stupid comments for mothers of two boys about mud, aggression, volume of food consumed. Additional stupid comments for mothers of two girls about bitchy teenage years and bathroom hogging.
Three: Assumptions you were only having a third to get a boy/girl. Comments about being stretched too thin, middle child syndrome, etc.
Four of more: When are you stopping. Are you addicted to babies, yada yada.
Big and short age gaps also get their own set of comments regardless of the combination of children.
Just about the only group who escapes are those who are 'clever' enough to have a boy and a girl 2-3 years apart. They can be the worst for the comments above though IME.
You do what is right for you, your partner and your family. The only thing I would say is that you have to be happy with the choice for the whole of the child IYSWIM - not having to do baby again also means not having another child. You have to want (or accept) both. I am not keen on babies, but did want more children. It goes the other way too, no one should have another baby to have a baby, but to have another family member long-term.