1:9 - 45-69gr ,1:7 - 45-80gr, Why limit yourself. As far as the buffer tubes, it is personal preference. I prefer a Mil-Spec tube. I have had two buffer tubes that were not mil-spec(both Bushmasters), they worked fine but had more "wobble" in the standard carbine stock. I have also had one mil-spec that would "catch" while between positions(Colt, hence my customer support issues).
I am in no way advocating Colt, the OP asked from the two he listed, which to get. I gave my opinion. I will never buy another Colt again. But if I am going to pay for an AR, I want a few options WW does not offer(at least in the basic model). The Chrome-lined barrel is the deal breaker for me. If I buy a carbine style rifle, I am going to stuff as many rounds through it as possible. The Chrome-lining is your friend if you plan on shooting it a lot. While to some it is not a big deal, to me it is a huge deal. It is my money, I am very picky about how it is spent. Again, remember that mine is just an opinion, so are the others. Take it all with a grain of salt.
" The strongest reason for the people to retain the right to
keep and bear arms is, as a last resort, to protect
themselves against tyranny in Government...." - Thomas Jefferson