From a standpoint of personnel philosophy, Eagles defenses over the past decade have been very similar to Cowboys defenses during the 1990s.
Aside from the obvious alignment similarity (4-3), both defenses value speed over any other attribute, and both refuse to pay a premium for linebackers. With the notable exceptions of the Cowboys' Ken Norton, Jr. and the Eagles' Jeremiah Trotter, linebackers tend to be of the plug and play variety -- players with a very specific skill set that is tailored uniquely for a particular system but is often a liability in other systems. Consequently, linebackers can be had cheaply. The success of both defenses is predicated largely on the defensive line; therefore, they place their emphasis there.
Comparing the modern incarnations of Eagles and Cowboys defenses is difficult because they utilize different alignments. However, here's my opinion:
1) The secondaries are a wash -- Hamlin is the most proven safety, but the Eagles hold an advantage at the second corner position where Sheldon Brown has more experience than either Jenkins or Scandrick.
2) Ware and Ratliff are more disruptive than any player(s) in the Eagles' front seven. However, the Eagles may have better talent throughout their front seven.
3) The biggest differences between recent Eagles and Cowboys defenses have been coaching and tenure of system. The Eagles have been using the same defensive system for a decade, and Jim Johnson is one of the best in implementing and deploying that system.