If you're interested in the public sector, choose WWS (and join me there - I'm in the incoming mid-career MPP class!). WWS is all about public sector careers, and that's precisely why they provide a full scholarship to all MPPs and MPAs.
The overall class size as well as individual class sizes are significantly smaller than HKS, so there's a lot more faculty interaction. In addition, Princeton doesn't have other large professional schools like Harvard (HBS, HLS), so there really is extra attention (and resources) on the WWS students, including career mentoring.
It's true that Princeton is in the suburbs while Harvard is at Boston's doorstep, but in both cases you will still be in the college bubble. I went to Harvard for undergrad and very rarely made it to Boston. Plus, Philadelphia and New York are still very close to Princeton (45 minutes / 1 hour respectively).
If you really can't make a decision, go to both schools' Admitted Students Weekend and then follow your gut feeling.