Married filing joint rates are better than head of household. From purely a tax standpoint, owning a house would be better. Having a child will give you a $3,300 deduction, plus a $1,000 child tax credit. However, in your situation, because of your income level, you probably won't get any of the $1,000 child tax credit (the credit begins phasing out when your AGI is above $100,000). If you own a home, your mortgage interest and property taxes will be deductible.
However, when you look at it purely from a cash flow basis, having a child would be better. Say you purchase a house for 300k with 20% down. Your mortgage may be around $1800 per month. The property taxes on a 300k home in NY would be roughly around $8000 a year. This means your payments per year would be over $29,000 a year. This also doesn't take into account costs such as water and sewer, garbage, etc. that you normally don't have to pay because your landlord pays it. Your landlord may also pay gas while you pay for electric. And what about the costs to mow your lawn, the opportunity costs for having to shovel snow, homeowner's insurance (this can be easily $1,000 or more a year), etc. So let's just round up and say that it will cost you $32,000 a year to own your home. Going back to the $29,000 for mortgage and property taxes, assume that number is your deductible amount. At the 28% bracket, that means a tax savings of $8,120 a year.
If you have health insurance from work, you would need to pay more to cover "family" rather than just "employee and spouse". Figure the difference might be $1,000 a year. Buying baby clothes, formula, and diapers, doesn't cost $23,000 a year (the after tax amounts of your house payments less the tax savings), your out of pocket costs of owning a home.