there are several reasons why the philosophy paper sounds better: it's current, it sounds better written, it shows development you've experienced since your BA, and you seem more satisfied with it. Length sounds like the only thing in favor of the older paper; quality is better than length (you can always add to the 10-pager, if you need to).
you don't tell us what the older paper is about (subject-wise), or which is more suited to your MA program. But in my opinion, a well thought-out philosophy paper should have appeals to almost any Humanities department.