I give an example of my previous client (from the UK in 2007). They basically added (as affiliate partners) Umbrella group of companies those were dealing in IT (Income tax) Contractor. Their website URL is itcontractor.com and they received more than 90% organic by "IT Contractor (keyphrase)" only by the way that time we could easily track organic keywords with traffic from Google analytics. Now I am not working with this client but now I have googled this keyword again and this site is still in top 10 in Google Uk searches. Now, Google is smarter than previous also it is very risky for EMD, but I must say there would be an advantage if we use keywords in our URL especially for Google maps listing.
I have also searched you keyword that you want to use in your URL and there are 3 mentioned below sites are in top 10 used keywords in their URL
Now come to your basic question for that you would need new-york-headshot-photography.com as I have read somewhere that Google understands separate phrase once you use - in your URL but another aspect newyorkheadshotphotography.com is easy to type, so you should select this. But it doesn't mean only using this URL you will be in top 10 there are many more factors and most important is content as test-ok stated here.
There would be still another aspect of the business that is branding so would also need to think about those aspects and take you call.
Some tips see the sites like
Amazone, eBay etc. Now it is up to you how you take this?
I am sure "Knowonespecial" and other members will come up with their suggestions so stick around.
You do your business I do mine because you are you and I am I If we meet it is nice.