A chrome lined barrel will have about twice the life of a non chrome lined barrel of about 15,000 to 20,000 rounds. Chroming is done after a barrel is rifled and the process strips some metal from the barrel before being chromed to bring it back up to tolerances. The lands and grooves of the rifling are not as sharp as on a non chrome lined barrel and tolerances can vary depending on how much material was stripped and how much chrome was applied.
The non chrome lined barrels are usually more accurate since bore tolerances can be machined to tighter specs. Most all competition barrels are non chrome lined.
The trade off is that the non chrome lined barrels will have a life of 8,000 to 10,000 rounds.