The study uses data of people per thousand between the ages of 20 and 34...the most likely age for couples to have issues. They then use data of how many people are married, how many have divorced, income disparity between the couples, starter home affordability rank, and the availability of counseling. They double-weighted the marriage/divorce factor and put half weight on the counseling factor.
Some surprising things: Texas cities beat every other state by far...Dallas is the number one best city for couples while Houston is number 2, Austin number 5 and San Antonio number 7. Milwaukee doesn't make it until 27, and seems pretty average in all aspects. Salt Lake City outranks every other for most marriages while the least city for divorce is Indianapolis. The cities that do the worst are Miami, Providence, Rhode Island (I hear it's a crazy place) and Cleveland makes number 40. Here's the full list.
One thing the survey had no way of including was the rate of infidelity and it's role in breaking up couples, which obviously is a common reason for the end of relationships.
On the other hand, Forbes also does surveys that prove which are the best cities for singles. With higher rates of singles each year, the list has changed from previous years. At the top are San Francisco at number 1 and New York City at number 2. Denver used to top the list but has now dropped to number 16. Here's the article on that.