The People's Court of Opinion sez stainless steel barrels are more accurate, or have the potential of being more accurate. Chrome-lined barrels are easier to keep clean in bad conditions.
I don't do any long-range bench-rest shooting, but I read that people who do all use stainless steel barrels.
Personally, I don't like the way stainless barrels look on an AR-15.
Unless you plan on shooting over 10,000 rounds, barrel wear should not be a problem with either one.