@JohnSSS - You’re also right to say that fit is the most important factor here.
In terms of fit, though, Williams offers a “one size must fit all” model, whereas Penn’s fit is much more flexible. You can’t get an urban experience at Williams. You can’t experience a top research university at Williams (taking classes at UMass Amherst, something Williams allows, isn’t the same). You can’t take classes in accounting or marketing or engineering at Williams.
You can do all those things at Penn, AND you could still take a bunch of classes at Swarthmore or Haverford College.
Finally, you present stats demonstrating Williams’ strength in placement. You fail to look at this, though, through a historical lens.
For a long, long time, Williams was undoubtedly a stronger school than Penn. It was more selective, had much better per capita exit options, was considered to be more prestigious, etc. Williams was really at the very tippy top.
Now, as rural schools have fallen a bit out of favor, and small LACs in particular (without the benefit of strong, direct pre-professional programming) have decreased in popularity, the landscape is a little different. Penn in particular has gained from offering an array of professional programming in an urban area. Stronger students come to West Phila, and UPenn’s placement is improving as well.
A case in point: http://www.vpul.upenn.edu/careerservices/20142015lawstats.php (usually about 10-15 UPenn grads go to Harvard Law a year), and, similarly, http://www.yale.edu/printer/bulletin/pdffiles/law.pdf (on p. 159, 21 Penn grads are at Yale Law, compared to 10 Williams grads).
Per capita, Williams probably still outdoes Penn, but the gap isn’t nearly as large as it used to be.
As I stated earlier, if the OP can drown out the white noise at UPenn, it’s an excellent choice. The experience can be molded. If the OP wants a small elite LAC, though, there really isn’t a better choice than Williams.