I had the same curiosity awhile back and i found info on the net on several forums (THR, m1911.org). But the debate tends to develop into a "new design vs traditional design" rather than a "pro vs con". On the other hand, I don't see too many folks complaining about the external extractor as it looks easier to maintain and adjust, but some say it has more failures (loses tension quicker). Read for yourself. It seems only the high-end (S&W, Kimber, Dan Wesson) pistols feature this and it is marketed as an improvement to the 1911.
For casual shooters, I suspect there is no difference but perhaps someone here has first hand experience and can elaborate further.
hb