@4101297 College Factual and Niche have some IR-specific rankings you might wanna look at. (CC won’t let me post the links for some reason).
And here is the Shanghai ranking for polisci rankings. (widely seen as the most respected academic/research ranking).
http://www.shanghairanking.com/Shanghairanking-Subject-Rankings/political-sciences.html
Regarding location Ann-Arbor is much prettier. it is a pretty college town. Penn is well integrated into Philly but also has a cohesive campus that has a lot to offer and has been really transformed over the last two decades. The proximity to downtown Philadelphia and the defined campus feel provides the best of both worlds (campus community and offerings of a big city).