I'm looking to get something to bridge the gap between my 20" AR10 and 16" carbine.  This rifle will probably be equipped with either a TA31 or compact ACOG, and a Magpul stock.

I don't think I want a 20" barrel on a .223 when I already have the AR10, so I'm left with the choices of either a 16" (mid length) or 18".  I will be using 75 grain rounds, so I need at least a 1:8 twist

For the 16" option, I could use one of the new chrome-lined 1:7 mids that are becoming available.

I seem to have missed the SPR craze, so I don't really know much about the available types of 18" barrels.  Are any of them chrome lined?  Where can I see some of the available options?

What do you guys think about this choice?  What does an 18" barrel really offer over a 16"?