My wife wants a 4th baby, but I don't.

We have been talking about it for the last few days (talking strongly).

I have raised points such as:

• We will get less time to spend with our current kids.
• The age gap between the first and the last will be too wide.
• It will cost more money.
• She will be out of work longer.
• We will need a bigger house. And we don't even have our own house yet (we are still renting).
• We will have to start again. Sleepless nights, nappies, feeding, new cot, car seat, etc etc.

She says:

• She feels like she is missing something.
• She has always wanted a large family.
• Things will be the same regardless of having 3, or 4 kids.
• She agrees that money will be tighter, but wants to push through it.

Our current kids are 9 months, 2 years, and 4 years. We are young married couple (25), and I have a fairly decent job.

What would be the pros and cons of having another child?

How can we rationally talk to the other about having/or not having another child?

And what should we do if we cannot agree?

(sorry I don't really know what to tag this).