Stainless barrels break in sooner than chrome-moly, but quality chrome-moly barrels can outlast several stainless barrels used for rimfire benchrest.
I have not found a significant difference in the centerfire barrel life between chrome moly and stainless and I have no clue as to rimfire.
While dining in the Shooter's Mess at Camp Perry this year, (on all you could eat grilled Ribeye steak!) I sat across from a former Small Bore Prone National Champion and asked him how many rounds he had put through his barrel. He said about 700,000!.
Maybe the benchrest shooters are seeing things that are inside his hold, but I before I have heard estimates of the barrel life of a rim fire match rifle that were around 250,000 rounds. This was the first time I heard of anyone firing over a half million rounds through a barrel.
I hope I live that long.