What are you asking? If you're asking if there is a ballistic difference, yes, there is. It is a fairly small one, but it is tacked onto the also small-ish ballistic differences from dropping from 20 to 16 inches. At some point, the ballistic penalties add up, and for me it is right around 16" (as in, I'd prefer to not to go too far below that). Add in the PITA it can be to remove the "permanently attached" FH if you want to do anything with the barrel, and the very reasonable advantages of going with a midlength gas system on a 16" barrel, and I personally don't find it worthwhile to go the 14.5" route. That, however, is me. Also, if I found a nice upper for a nice price in 14.5"/perm-FH configuration, I would not pass it up. Like I said, the differences are small.
What I REALLY don't get are the silly 10.5" barrels with looooooooong FHs. What the heck is the point?
Mike