Pros & Cons can get into a long debate. Kimber has gone to external, then back to internal. Not sure of their present status. My 1911 is a pre-70 Colt with internal just like JMB designed. My personal view is that internal extractors are just fine. It seems you did not hear about extractor problems in the old days with the GI issue .45's. Even though my internal extractor is one piece, I do take care to removed it for cleaning and keep it lubed. Never had a problem..including never having a problem with an old Remington Rand I put thousand of rounds through. I do have other semi-autos (not 1911) with external extractor and they also work fine.
IMO, properly made & tuned internal extractors work as well (and as long) as any external extractors.