One of my profs did his PhD at the University I want to apply for my math PhD. Should I get a recommendation from him?
As a tiebreaker, it might be nice to have a strong letter from someone who went to the target university, especially if it has a highly specialized or unconventional program.
However, yours is not such a marginal case. You stand to benefit more by getting a letter from a professor who knows you closely and can say positive things about your research ability.