For having an occasionally adversarial relationship, banks and credit unions are more than a bit incestuous.

Plenty of credit union personnel, right up to the chief executives, got their start at banks. And although they pride themselves on having their own institutional culture, credit unions are keen to use ex-bankers’ expertise while, they say, staying true to their roots.

Banks, on the other hand, often complain that larger credit unions act exactly like banks, except they happen to have a huge competitive advantage in their nonprofit status.

Over time, credit unions have gradually adopted more sophisticated practices. In 1977, legislation gave credit unions the ability to make mortgage loans, and further expansions have followed.

Now, credit unions can have commercial lending and mortgage departments that compete head-to-head with banks. Currently, they’re fighting for greater freedom to lend and raise capital, as their banking peers are able to do.

But credit unions and consultants say the ex-bankers in their ranks aren’t directly helping steer the industry in that direction. Instead, market demands and credit unions’ own growth have pushed them to evolve in a certain way.

Of course, some examples can show how ex-bankers have more deliberately nudged credit unions on a new strategic path.

More credit unions have warmed to the idea of commercial lending. In some cases, that’s because a laid-off bank loan officer approached the institution, pitched the idea and offered his services, according to C. Dennis Beaver, owner of New York-based Hill Creek Consultants, which specializes in commercial lending for credit unions.

Some credit unions on the West Coast have even gotten into serious trouble lately because commercial real estate lenders sold them on the idea years ago, during a time of mass bank consolidation that left many laid off, Beaver said. Then, the commercial real estate bubble burst, with well-known results.

But that kind of result is rare. More often, credit unions get into commercial lending because they grow large enough to have a few sole proprietorship entities on the books, and eventually start loaning money to them for their commercial enterprises. It often snowballs from there, Beaver said.

Peter Muise, CEO of New Bedford’s First Citizens Federal Credit Union, scoffed at the idea of ex-bankers enacting some broad cultural shift in the industry.

“Don’t make the mistake to think that banks are run one way and credit unions another,” he said. “It’s the individuals that run those institutions that run them one way or another.”

Muise himself worked at a bank for years before joining First Citizens more than 15 years ago, and says many credit union executives got their start the same way.

It’s far rarer to find former credit union executives working in banks, credit union officials said, because there are simply far more and larger banks, and consolidations tend to create job-seekers that eventually apply at credit unions.

Credit unions searching for new talent often consider bankers looking to make the transition, but only up to a certain management level, said Beverley Purtell, vice president of human resources management for the Massachusetts Credit Union League. Purtell advises many credit unions on their hiring searches, and said nobody really wants to hire their new CEO straight from a bank.

For one thing, bankers often require larger compensation packages than credit unions are prepared to offer, although the institutions try to be competitive. They also play up other, less-tangible benefits, such as a gentler, lower-pressure environment, she said.

But more importantly, there is a significant cultural divide between banks and credit unions. Banks are rewarded for risk-taking, while credit unions are more conservative by nature.

However, credit unions are happy to hire qualified bankers for middle- or upper-management, Purtell added. Often that experience has made them adept at selling financial products, and Purtell is always particularly interested when applicants say they’re disillusioned with some banks’ high-pressure sales tactics. If they express a desire to be more customer-oriented instead of sales-oriented, she said, that’s a good sign they’ll do well at a credit union.

Paul Beaulieu, senior vice president of operations and technology at Marlborough-based St. Mary’s Credit Union, worked in banking for 30 years before being laid off after a consolidation, and joining St. Mary’s in 2008.

It’s true there’s a difference between the two types of institutions, he said. Commercial banks consider their shareholders, customers, employees and communities, but credit unions don’t have shareholders to consider, and put more emphasis on members.

But the differences are hardly stark, he said. Community financial institutions in particular have to be customer-service oriented.

“Even in a community bank, if you don’t pay attention to the customer, chances are it’s going to affect your success as an organization,” he said.