I have a pre-ban lower receiver and just built up the lower receiver assembly.  I'm looking at the upper assemblies and are wondering - is there an advantage to buying a pre-ban upper to go with my lower?  I live in Georgia, so there's no issues that I'm aware of with respect the law here.  

If you live in a free state there are no issues at all purely from whether it was made before or after a certain date that the Democrats made up.

Buy what you want on features, brand, price or whatever else.

what's the difference in the barrel assemblies themselves?  is there an advantage of pre over post ban barrel assembly?  to my novice eye, they look the same??

thanks!  I was typing my questions while you were typing the answers.  I greatly appreciate the help.

Quoted: A pre no ban upper will normally have a bayonet lug and flash suppressor. The flash suppressor you want, they dramatically limit the amount of flash the AR gives off in low light and how much it affects your vision. The bayonet lug is fairly useless for civilians. I think there are some lights that mount on the bayonet lug. Most of us buy a bayonet, stick it on there when we get home from the gunshow think "Damn that looks cool!" then take the bayonet off, throw it in a box in the closet where it'll sit til our great grandkids find it.

+1

Bayonets have almost become an afterthougth for the military as well.  Mostly we just want them because it pisses of the Liberals.

The difference is mainly the threaded barrel.  If it isn't threaded for a flash suppressor, it's worth less if you ever want to sell it.  Also, if you shoot in low light, you'll want a flash suppressor.  It costs at least $50 (usually more) to send a post-ban barrel and have it threaded by a gunsmith.  If you have a choice, buy one with a threaded muzzle or require a big price discount if it's post ban.  

Quoted: The difference is mainly the threaded barrel.  If it isn't threaded for a flash suppressor, it's worth less if you ever want to sell it.  Also, if you shoot in low light, you'll want a flash suppressor.  It costs at least $50 (usually more) to send a post-ban barrel and have it threaded by a gunsmith.  If you have a choice, buy one with a threaded muzzle or require a big price discount if it's post ban.

Only 16" + barrels can be threaded (NFA exceptions).  Barrels shorter than 16" must have the Flash Suppressor or Muzzle Break permanetly attached making the barrel 16"+ inches over all.

Some muzzle breaks reduced flash to a certain extent but they are not as effective at doing this as an actual Flash Suppressor and muzzle breaks protect the barrel crown just as well as a flash suppressor.

Friendly FYI: Due to the current circumstances the phrasiology of pre/post ban has largely been dropped in favor of ban/no-ban in states where the expiration of the AWB had any impact.