I'm sure there are data on this that could be used to answer your question. Not having seen it, I can offer the following points.
Younger GMAT aspirants are generally closer in time to using math and studying in general in high school and college. Their fresher memories of the topics and the fact that they have more recently been involved in academics can be advantages for them.
On the other hand, older GMAT aspirants with more work experience tend to have been project management skills, which tend to lead to GMAT success.
So, there are offsetting factors.
Accordingly, the strongest performance could be that of people just out of school and those fairly long out of school, because people in those two groups have strong advantages in their two ways.
In any case, effective prep will lead to a high GMAT score for anyone. So, perhaps the most important factor is determination since, with determination, you can keep pulling levers as necessary and achieve your goal regardless of any advantages or disadvantages you may start with.