If we drafted a DE in a 4-3 defense at #3 we would all be ecstactic right now because that means that we get to see sacks and QB pressures and all the things that make defense great. The 4-3 DE is probably the most important position on that side of the ball, (Jared Allen, Freeney, Mario Williams, etc) will make or break the play of the entire defense.
So when we grab the two best 3-4 DEs it's met with a bunch of yawns and disappointment, and some "wait and see" type approaches. But, assuming everyone on here is just a touch above an average football fan, we can say what is boring yet completely true and that is "Football games are won at the line of scrimmage." But first, lets look at how a 3-4 DE works under the radar compared to highlight seeking 4-3 ends.
A 3-4 End plays a huge role in the 3-4 defense and is rare to find their size as they must have height, size, and mobility to occupy the O-tackles. The positives of a 3-4 are that you have some big, strong, disruptive lineman that free up your LBs and secondary to make plays. The linebackers in a 3-4 are much more focused on their roles, either stopping the run or rushing the passer (in really general terms). Another 3-4 benefit is that it is easier to find LBs to fit your system because you are able to use their athletic benefits more one-dimensionally. This means we can find them in late rounds or in free agency if we have the proper talent evaluation. So if we really did get the two best 3-4 DEs in this draft, the most versatile and well sized guys, then why wouldn't we be cheering? These guys are pretty difficult to find outside of the early rounds in the draft.
We're going to see our OLBs get straight QB pressure, opposing running backs chipping away for 1-2 yards a carry or getting stuffed behind the line of scrimmage. We're going to see tipped balls turn into interceptions, cornerbacks and safetys who won't have to glue to their receivers for 15 seconds.
It may not look pretty now, but it's going to feel a lot better to hold opponents back, and not watch running backs bounce off of our guys and rack up career yardage against us. If these guys pan out, we may be doing far more to improve our weak defense than we have in the recent past while it may not feel like it at all.