Someone who has a weak head at learning has the exact same mitzvah rabbah, and receives the exact same schar, and is as valuable to the security of Klal Yisroel, as the person who is a terrific learner when both put in the same full time hours of Limud Torah.
There is absolutely zero basis to assert that the better learner has more right or is more suitable to be a Kollel yungerman than the person who cannot learn nearly as well.