[darkgael]

".. is a 16 inch barrel favorable? I love RRA, the quality and factory preparedness they deliver the rifles with sells me over remintgon, DPMS, etc... What about twist rate: I have read that a 1:9 twist is best for the .223 in a 16 inch barrel. I'll most likely go with another AR just looking for feedback."

I'd go with the 20" barrel. Longer sight radius. I suppose, though, if you are shooting through glass, that the 16" will be adequate. Rifling - what you need depends more on what kind of bullet you are using than the barrel length. If you are going to be shooting mil. surplus type rounds, then the 1-9 should work.
Note: the High Power Service Rifle guys, shooting at the 600 yard line, are using bullets that require 1-7 (or faster). My own AR works well enough with a 1-8 twist and 75/77 grain bullets. That would apply to 500 yard targets, though I suspect that a man-sized target is more forgiving than the high power bull (Maybe? Maybe not.).
Pete