You have every reason to have a chrome lined barrel in an AR15 if you plan to shoot non-corrosive ammo.
IF it's a plinking/tactical gun, that are you not demanding Sub-MOA accuracy out of, as such, don't want to baby the bore and have easy maintenance, a chrome bore is so much easier to clean. They typically do not collect copper as much as other bores, carbon comes off much easier, and they tend to be longer wearing.
I had a chance to play with a bore scope, I compared 3 barrels with the same-ish round count. The chrome bore looked the best.
So, to sum up your question. Chrome will be less accurate but lower maintenance, SS will be more accurate but higher maintenance.
SS isn't that bad tho'. If you break them in properly, they can come out pretty smooth and as such clean up pretty fast.
Any standard steel bore I've owned in a rifle, will take more time to muck out the fouling, and just gets smeared with copper fouling.
They tend to be the most accurate, but at the price of high maintenance.
The SS bore I have, cleans up pretty fast, but not as fast as Chrome or Nitride. It will collect some copper but not as much as a standard steel bore.
Some circles argue that Steel bores are much more accurate then SS.
The Nitrided bore I have, is pretty resistance to copper fouling. I've never cleaned copper out of it, but my scope inspection shows that tho' some did build up, it's not anywhere near as much as you would expect given the round count. It cleans up fairly quickly. Heck, if I use a good clean burning ammo, I can have it cleaned in just a few patches.
The Chrome bore I have cleans up very quickly. Like the Nitrided, it can be done with a handful of patches. Meanwhile, I ran copper solvent thru' it in the beginning to see what I would be dealing with, and the patches showed no green/blue. I never copper cleaned it again. 2300 some rounds later, the bore scope shows no signs copper fouling.
