In themselves, neither has an absolute advantage over the other in the terms you enquired about (career prospects, alumni network, educational experience, research and internship opportunity).
CMcK might have a very slight edge over W&L in terms of educational experience IF you factor in cross-registration at Pomona
W&L possibly has a very slight edge over CMcK in terms of alumni connections, esp if DC is a goal.
Not possible to discern even a tiny difference for either research or internships opportunities. As I posted earlier, what the student actually does- the relationships they build, the way that they look for and take advantage of research/internships opportunities, etc- will matter much, much, much more than any of the above possible differences.
What could matter a lot is what happens after college. Common paths from policy or international economics includes NGOs, policy institutes and think tanks (all of which will require grad school), or government agencies (which won’t pay well).
So, IF the cost of CMcK is equal to the cost of W&L for you, then go ahead and pick based purely on personal preference.
Or, IF your financial resources are such that any difference in cost between the two is completely incidental to you, again let your son pick solely on personal preference.
But, IF paying the difference means 1) debt or 2) less ability to help them with the transition to professional life (helping to subsidize a first apartment, helping with grad school), then follow the money.
*note that consulting or IB (current faves with a lot of HS students) value prestige, and neither school outranks the other for that