It all depends what you really want to do with the rifle and what the terrain is like in your AO.
If you are going to use your rifle for TSHTF use, but lived in a city or other area with dense veritation or obstructions that inhibit shots past 100 meters, than the 14.5" barrel will be fine.
But if you live on a ranch or places with lots of open area and at ranges beyond150 meters, stick with the 16" or even better yet, a 20"er.
the rifle that I am going to build soon (pre-ban) will have a 14.5" barrel with affixed phantom flash hider. I picked the 14.5" barrel over longer lengths under the premise that even though my area has lots of open space and farm lands with many fields, if I find myself ever needing to use the rifle, I will be doing so at ranges much less than 100 meters. I would be taking an defensive role and would not be out to pop every target between myself and the range of my weapon. My main goal will be to survive as long as I can, and picking fights will probably lessen the probibility of my being able to survive.
becides, if you really want to shoot that far, get a .308 [;)]