That's the debate in a nutshell - an effective pass rush v. "a pass rusher".
Basing your pass rush on one premier guy takes both those advantages away by giving the offense someone to key on.
Which is absolutely fine on third down in a likely passing situation. There is nothing wrong with a dedicated pass rusher that the offense will have to scheme against. A third down back and the emergence of the nickel corner as "quasi starters" in the league is predicated on the importance of third down and converting them to sustain drives. The Patriots are vulnerable via air attack and do poorly on 3rd downs.
The game, esp defense, is about trade offs. When the Patriots run their "bend don't break" type of defense, it's a trade off. It's saying we don't want to give up the big play but we will give up something else. Elite pass rushers all come with some kind of trade off or deficiency.
If the offense keys off of one or more guys, then good. Maybe it frees up another player to hit the QB. Maybe it rattles the QB if he has nerves. Maybe it forces the O line go into max protect, reducing the number of receivers by one.
All around players, pure three down front seven players are very rare. The Pats, like other defenses, use different packages and personnel to account for the fact that the players do have strengths and limitations to consider. You have to work with the talent you have.
Andy Reid, IMHO, forced his team to struggle badly for years offensively ( relative to what they could have been) by
- Drafting poorly at WR for a very long time ( this has changed of late)
- Running an extremely complex offense for his WRs to learn
- By the time a WR might learn his system, they'd be knocking on the door of their second contract
- Using a pass heavy offense despite having a QB who was not fully suited to the WCO and was not the most accurate QB in the world
- Outright refusing to run the ball, even when his QB was older and hurt, even when his D was struggling.
That offense was saved by McNabb and Westbrook for a long time.
When your scheme is not congruent to the realities of your personnel and limitations, it's a plan to fail.
Belichick spent countless pick and after pick and money and resources to beef up his secondary, but his current teams can't hit the QB. No secondary, no matter how talented, is going to be able to cover a play forever. He also didn't get great returns on some of his LB acquistions ( Burgess, Thomas, Colvin) If Belichick wants to be as hard headed as Reid, then fine, but it doesn't help the team in the long run. Honestly at some point, he's going to have to accept personnel with some limitations, maybe more than he'd like, so his D can actually consistently hit the QB.
It's almost like guys want no tradeoffs whatsoever in exchange for a pass rush when the reality is the entire game is built around tradeoffs period. Maybe Clay Matthews isn't the best all around linebacker, but I can tell you this, if Mark Sanchez got hit four or five more times really hard by a Matthews type, that game might look different.
Sometimes one premier guy who excels at only a few things is what you need to change the complexion of the unit.