As Eagles fans, we have not witnessed enough of the 3-4 to realize how it changes your options. In the 4-3 defense players are what they are seen as on the roster. It is harder to create packages based on your players versatility. This is not saying Trent Cole was for example, not able to drop back in coverage. I am simply saying there is a broader span of options of what you can do with your personnel. This is why versatility is key to a successful 3-4 and 4-3 under defense.
Honestly on a side note, we here on BGN make our roster 53-man depth charts on defense for one type of defense because we are use to it under Andy Reid. However, we should make our defensive depth charts have the same players but have their roles on defense change. Anyway my depth charts show how we can use our personell effectively for different scenarios.
4-3 Under (Not a full defense or 3rd string, just main rotations)
RDE- Brandon Graham-Trent Cole
WDT-Fletcher Cox-Clifton Geathers
NT-Antonio Dixon-Isaac Sopoaga
SDE-Bennie Logan-Trent Cole
CB-Bradley Fletcher-Carry Williams-Brandon Boykin- Poyer
FS-Nick Wolff-Patrick Chung
LDE- Bennie Logan
ROLB(Predator)-Brandon Graham with an occassional spice of Connor Barwin
LOLB-Connor Barwin-Kenny Phillips on 3rd and Longs similar to Charles Woodson
CB-Bradley Fletcher- Cary Williams-Brandon Boykin
FS-Earl Wolf in the box with Chung on obvious passing situations
I for one am not sold on Cedric Thornton because he has not proven anything to me in the past years.
The main upside of the 4-3 under is that of the weakside of the O-line. It does most of it's damage on the Guard playing that side. In the 3-4 vesatility plays a big part because it allows for Phillips to be what he was before his injury plagues. It makes people have to account for him at every single moment. Basically, he is the "Predator" of the defensive backs. Sorry if you feel this is not complete or if this should be a fanshot.
Feel free to comment, criticize and add your own.