If he wants to pursue a Ph.D. in pure math, undergraduate research and graduate-level courses as an undergrad will give him a huge advantage in the application process. My daughter has run into many prospective Ph.D. students who feel their LAC background has put them at a disadvantage in the application process for top-tier programs because of the lack of undergraduate research and advanced coursework. For that reason, and because UM-CP is known as a “math” school, I vote for UM-CP over W&M.