But according to the largest insurers, services beyond the buyout deal itself are becoming increasingly important, with the differentiator of "administrative capability" looming large.

Prudential, the largest, with $60 billion in retiree pension liabilities under management, has released a series of white papers that look at the service delivery capabilities of an insurer, and why it's essential for a plan sponsor to evaluate those capabilities when it's considering a pension risk transfer provider.

Here's a look at five factors Prudential says are vital for plan sponsors to take into account before making that decision.

1. The fiduciary element.

Plan sponsors must, of course, perform due diligence, says Prudential, "ensuring all fiduciary standards have been met, the right questions have been asked, the proper issues have been considered and all concerns have been fully disclosed and resolved."

But that's only the beginning of the process of derisking.

2. Customer service—for the participant.

It's not enough to make sure that the RTP understands the financial and regulatory aspects of the transaction, Prudential says.

Plan sponsors must also consider how plan participants will regard the customer service provided by the RTP.

This includes such factors as understanding the retiree population, demographics, climate and culture; making sure checks are consistently delivered on time; prioritizing retiree needs and expectations; and anticipating customer needs.

3. Communication and education.

Sponsors, says Prudential, must make sure that insurers seeking to undertake risk transfer are able to provide both education and communication opportunities to retirees in a variety of ways, so that retirees can access it via their method of choice, whenever they need it.

4. Participant concerns.

Plan sponsors should look at how an insurer plans to address any potential misgivings or anxiety on the part of the retiree.

While providing plenty of supporting information on the security and stability of retirement payments is essential, there's also the matter of proactively reassuring retirees about the transfer itself, the company undertaking the responsibility and any changes anticipated in the payment delivery method or timing.

5. The process itself.

The move to a new provider of benefits should be as seamless as possible from both the plan sponsor's and retirees' points of view.

How smooth will the process be? What is the transition process like? How will the insurer address both sponsor and retiree concerns as the switchover is made?

How easy will the process be, for both sponsor and retirees? Will there be delays?