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? The prof is quite famous (lots of publications and even a Wiki page). His doctoral advisor is also quite famous (still is part of the faculty of the university that I want to apply to). Would a recommendation letter  have a significant impact on my application?
Alternatively I can get a letter from another prof which will be probably a little  stronger. Which option would be the best for me? Basically would the other prof's letter carry more weight since he got his PhD from the university I am applying to.
I am applying to a top 3 institution, (if that makes any difference).
Thank you all in advance.
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.