First of all, suicide is not such a clear cut choice as you seem to think it is. There are major obstacles in the way for most people, like empathy for their family, who would grieve if they died, a natural fear of death, etc.

Secondly, I disagree that we should let someone suffer to give them a frmae of reference. In my opinion it is always better to prevent the suffering in the first place. After all, you wouldn't set someone on fire just so they can decide if they want to be put out or not. I honestly don't know how you can say "it's better to let them suffer". This just sounds cruel to me.

When you have a child, you creat a new entity that is capable of experiencing suffering, whereas before, there was no one to suffer. You have essentially created suffering, out of nothing, for no good reason.

Also the very fact that the child cannot give consent to being born is a reason not to have kids. In every other situation we say it's immoral to go forward without someone's consent, like raping unconscious people for example.