Frankly speaking, the average homeowner confronting a 2AM break in, half asleep and in a defensive posture, won't know the difference between 14" or 18", nor would it matter. One is no more or less effective than the other at 2AM. For the "grunt or jarhead" going door to door in an offensive posture, yeah the 14" is a plus.
Then there is the NFA issue. Once you have registered your once 18" barreled M4 to a 14" barreled M4, it will forever be an NFA item. Simply put, you can't just swap the barrel back to 18" and hope to sell it to the local gun shop or gunbroker. It will have to go to a willing FFL class 2 or 3 sot.
Having a 14" is mostly a status symbol for most of us, and yes, I have a small NFA stamp collection, and no, I probably would not go that route again.
My 2 cents.........................