Another vote for Top of the Rock. Did them both on a trip a few weekends ago. Wasn't overly impressed with the Freedom tower, although a heavy fog also dampened the experience. Top of the rock is just more centrally located as previously mentioned, so you can get better photos of central park, and the Empire state building. It also does have the extra outdoor level that does not have the glass blocking your shot. Also maybe just because it's fairly new, but the Freedom tower was so incredibly crowded. It was hard to even snap photos or take in the view without someone wanting to jump in front of a window for a selfie.