I too have heard this same thing from my local gunsmith. However in questioning him further to get his reasoning his preference became apparent. His reasoning was that Stainless-Steel is harder to machine than Chrome Moly Steel, and it wears out his tools quicker. GIven that he reasoned that it would also be harder to rifle Stainless-Steel Barrels without the Rifling Cutters chattering causing a bad barrel.
The more and more I talked to this gunsmith it became more apparent that he just did not like working with Stainless-Steel period.
As for my own personal experience, I have had both Stainless-Steel and Blued Steel Contender Barrels both from T/C and Custom Barrels. If there was a difference in accuracy between the two I never found it, and to be honest I would imagine that the differences from barrel to barrel have more to do with it than Stainless-Steel vs Blued Steel.
Larry