We didn't have great success running the 3-4, but I think it is much easier to find players to fit the 3-4 as opposed to the 4-3. We tried for years to find good 4-3 defensive ends and whiffed and missed several times. 3-4 ends are much easier to find. The 3-4 also seems more schematically more versatile.
The problem we had with the 3-4 is that we never invested in the space eating run stuffing nose tackle that the scheme requires. We valued sacks from the NT position more than double teams and ability to collapse the pocket that most teams want from the 3-4 NT. I think it is much easier to invest ONE premium pick on a stud NT than it is TWO 4-3 defensive ends, who don't grow on trees anyway.
That's what I originally thought, but after years of watching the Cowboys run the 3-4, I now disagree.
The 3-4 OLB, especially the Strong Side OLB, is a difficult position to play. I requires a 3 tool guy that can play coverage, rush the passer and be strong against the run. That's a difficult combination to find.
The 3-4 DEs are usually a minimum of 6-4, 295. If you take out all of the DL in this draft that don't fit that criteria, then you remove about 3/4ths of the players.
It's hard to find ILBs that are big enough to take on OGs consistently and also have any amount of coverage ability.
The 4-3 under that Marinelli primary uses, seems like the easiest to find player to fit. The WDE can be a smaller guy and you don't have to try to find a guy that is both big and super quick guy like you need in the Giants 4-3. The 3-tech DT can be a smaller guy than is desired for other 4-3s and for 3-4s. The 1-tech does not have to be a super big player like a 3-4 NT. The SDE does not have to cover like a 3-4 SOLB an therefore it is easier to find a guy that can stop the run and rush the passer without also having to play coverage.