Consider selling point or unique selling point ("unique" if you want to emphasize that you believe this attribute makes you stand out from the competition). This seems to be common in résumé writing advice:
This site has an example:
When interviewing for any position [...] you need to know what differentiates yourself from all the other candidates. In other words, you need to understand the importance of utilizing your unique selling point.
Similarly, from employment site Monster:
When a company is determining how to advertise their products to consumers, they focus on its unique selling points (USPs) - the things which make the product different from any other. It may be that it is smaller, lasts longer or tastes better than its competitors. The same principle applies to you when you are applying for a new job.
You need to think about your unique selling points. What is the one reason that an employer should hire you above all other candidates? What can you bring that is unique or where can you add value to the position/company? What skills and experience do you have that will meet their needs?
This makes it clear that your [unique] selling point is not necessarily a personal strength, but can include specific experience. This would make it broader than "greatest strength" and fit your examples of research record or background.