I'm attempting to decide which to purchase for a patrol rifle.  I've narrowed it down to the two, and hope to tap the huge knowledge base here for your opinions.  
If I read the descriptions on Bushmaster's website correctly, the only significant difference is the barrel length (14.5" + flash vs. 16" + flash).  Would the extra 1.5" in barrel length be significant, am i missing some other major difference between the two?
Any and all advice/opinions will be helpful.

The 14.5 would have the Suppressor/compensator permanently attached unless the weapon is a registered SBR(Short Barreled Rifle.  With the 16 inch barrel, you can have the threaded end so you can change out from Flash Suppressor to compensator to sound suppressor(if you can legally have one)

The 1.5 inch difference will give you a different velocity.  I think I remember hearing something around 50 fps or maybe it was 90.  I forget exactly.