Hello,
Great choice for your AR. I purchased mine last November and it arrived early January. RRA makes awesome rifles and I know you will love it. As far as the chrome lined barrel I went without it mainly because they were behind in chrome-lined barrels and I didn't wanna wait! lol As far as the advantages, I have heard you need it and you don't. Everyone here had their own opinions there. I think you just have to go with what you feel more comfortable with. I was told and have read for the average shooter that a non chromed barrel is more than sufficient. I don't shoot mine a whole lot and I clean it right after every shoot. I think the biggest pro for the crome-lined barrel was that it is suppose to be easier to clean. But, mine AR has been pretty easy to clean anyway. So, whatever makes you happy. You will be happy whichever route you go. Now, if you are gonna go shooting in the rain and mud and not cleaning your rifle, then I would say, Get the Chrome..... Just my opinion.... [:D]
Happy Shooting and good luck with your new rifle....