You wont lose a bit of accuracy and the weight difference is nominal. The primary difference is that bullets lose velocity coming out of the shorter barrel.
Are you familiar with milspec ammo requiring a specific amount of velocity to fragment? If not, check out the ammo FAQ at the very top of the ammo forum. BRIEFLY, milspec ammo generally will make somewhat dramatic wounds when traveling at least 2700 fps. At that velocity or higher the buller will fragment into many pieces, creating a much larger wound than the actual bullet size would suggest. As it loses velocity and drops below 2700 fps, it will lose its ability fragment reliably. The bullet wont fragment at all below 2500 fps.
So at what ranges will the bullet be able to fragment is primarily dictated by barrel length. A 16" barrel will be good out to roughly 150 meters, a 14.5" barrel will be good out to roughly 100 meters.
A 16" barrel with a Phantom flash suppressor will be just slightly over 17.5" long. A 14.5" barrel will be just slightly over 16" long. The 14.5" barrel is slightly more handy, and, if it matters to you at all, will allow the use of a bayonette, whereas the 16" barrel will not allow the use of a bayonette. Difference in sound will be rather negligable.
You will have to permanently attatch the flash suppressor to the 14.5" barrel. You will not have to permanently attatch it to the 16" barrel. There are the differences in a nut shell. There is no single best answer as to which is better, only which is better for you and your application of the rifle. Decide which differences better suit your needs and go from there. Me... I had to have both