I am not sure I like this decision (and I am certain MARSOC doesn't care if I like it!). The 9mm is an anemic round and I saw guys in Iraq and Afghanistan load up with as many as 100 pistol rounds on any given patrol. That is too much. If you can't hit it in 10 or 20 rounds, throw your pistol at it...you will be just as effective.
1. It's a pistol - last ditch weapon so you can fight to your rifle
2. Modern 124 and 147 grain (not +P) in my opinion easily get the job done in putting holes in our target (or keeping heads down)
3. It's a pistol.
As far as the military handgun program, I'm all for, immediately buying 1.4 million Glock 19's and calling the whole thing done for 20 years!