Great post Wayne, you outlined everything I had in my head much better than I can put it into words. The main reason I like the Shimano triple 6703 is based on that on/off principle. On/off for me is the difference in not getting dropped as the majority of cyclists I ride with are stronger. It's so fast and seamless to move from the 30 to the 39 when I encounter a grade change from double to single digits. After much experimenting (and $$$ spent on various sized chain rings) I've come to the conclusion I like what Shimano wants me to like, 52/39/30. It will be interesting to see what Campy has up their sleeve for the Athena triple since they appear to be dropping the old chain ring mindset of 53/42/30.
The rear shifting with Shimano is much lighter than it was while I used Campy (Chorus 10 speed 2008 era, Centaur/Veloce 2009 ultra shift). A lot of it can come down to how the cabling is setup and routed but the basic principle of shifting up or down the cassette is less stressful with Shimano in my opinion.