I'm glad that the estimable Tom Van Dyke brought up the issue of what is the best style of quarterbacking, in his comment on Rush, race, and Donovan McNabb.
It's an extremely important question, and I don't mean the boring race and politics angles, but instead the football one.
I think Hunter is correct to point out that McNabb has simply reached the stage in his life where he must become primarily a pocket passer or get continually injured to the point that he can no longer play well.
There's a reason for this. It's that there are two types of running quarterbacks: ones who run to pass, and those who run to run.
What do I mean by this? Simply this: There are scramblers who run to get out of trouble and try to gain yardage by running the ball themselves. And there are scramblers who run to get out of trouble and are still looking to pass.
The former can get you a few yards at a time, and maybe a first down. And they'll get tackled hard and often. It takes a lot of toll on their bodies, as we have seen in so many examples, most recently the pounding that Michael Vick has taken and the number of games he has missed in recent years. And these quarterbacks get you a few yards and maybe a first down, but not many big plays. They do occasionally get some big plays, but not many. And those big plays, as I'll explain below, typically come when they are able to show themselves as threats to pass—when defenses believe they must treat them as quarterbacks who run to pass. The quarterbacks who run to run have limited yardage gain potential, and can be contained by a well-disciplined defense.
Then there are the scramblers who are looking to pass. These quarterbacks can easily get you twenty yards or a touchdown, and it happens a lot. That's because there is a standard reaction by receivers and by quarterbacks who are looking to pass, when the QB is flushed from the pocket: receivers break long, and the quarterback can often, if he can buy enough time so that he can stop just long enough to get his back foot planted, chuck the ball up over the defensive back(s) for a quick score.
That, incidentally, is what makes blitzing a risk: it can lead to a sack, but if it doesn't, it often leads to a big play for the offense.
Because of these realities, the truly successful running quarterbacks—and the most successful overall—are those who run to pass. Probably the greatest and most successful NFL quarterback of all time, certainly one of the top three, Joe Montana, was precisely this kind of running quarterback. He ran to get himself just enough time to find one of his great receivers (and yes, first-class receivers are necessary to the mix, but not sufficient without a great QB) and get the ball downfield. He had a long and hugely successful career.
Montana's successor, Steve Young, started out as a quarterback who often ran to run, and it took quite a toll on him. Eventually, he became much more of a quarterback who runs to pass, and he found that he could do both: when he scrambled, defensive backs had to take a quick look at him in case he got past the line and linebackers, and that was usually enough time for him to get a pass to a receiver downfield. But if the DBs didn't bite, he could get big yardage on the run because there were fewer defensive players in the vicinity to elude.
Now, these are all tendencies, not pure categories, of course, but nearly all quarterbacks fall into one category or another. All "pure" pocket passers, for example, run a bit in order to get free to make a pass, but the fact that they can't beat you for big yardage means that the DBs don't often bite. I think that this is why, for example, Payton Manning has never won the big one and Tom Brady has done it three times and guys like Trent Dilfer have gotten Super Bowl rings: Yes, their teams had excellent running games and great defenses (these are pretty much absolute prerequisites for football success), but their quarterbacks were also at their best turning imminent disaster into huge success. When Manning is flushed out, typically the Colts get nothing but a two-yard gain and a punt. When Brady and even lesser guys like Dilfer get flushed out, they pass for a huge gainer or a touchdown.
I would suggest that success as a quarterback in the NFL goes as follows, from most successful to least successful: those who run to pass, pure pocket passers, those who run to run.
Strategy, hard work, and execution, not color, are what win football games.
As applied to Donovan McNabb, then, my advice would be as follows: don't sit in the pocket waiting to get hit. Get out of there when the pressure comes, and PASS THE BALL!