1:7 will shoot just about every available load in 5.56/.223 pretty well, including all the heavy stuff. 1:9 will excel with lighter (~55gr) loads, and will not generally shoot anything heavier very well.
Non-chromed barrels tend to be more accurate, but less shit-resistant. A chrome-lined barrel will be slightly less accurate (how much depends on the quality of the chrome lining), but more weather/corrosion resistant on the inside.
I decided to install a Wilson stainless 1/8 on my final project upper.....I have same barrel on my service rifle for competition.
End use is key. On my carbine build I used a chrome lined 69.00 barrel. It shoots as intended. Good enough.
OK, going with a 1:7 twist rate... Now, is it worth the extra $20 bucks to go chrome lined over non chromed.... Hmmmm....
Primary purpose will be for HD and zombies.
BCM has several good barrel options too. They have standard and hammer forged 16" mid's in stock, including lightweight, as well as a bunch of other stuff.