What I don't think has been mentioned on this thread yet is that the electronic shifters auto-trim the front to align with the rear FOR EVERY GEAR. That's not possible on an indexed mechanical system: my DA double has three or four indexes, my Tiagra triple I think has five indexes, and our Campy Chorus/Mirage quad has maybe twelve. The electronic ones have 20.

I've told our tandem dealer to order us an electronic group as soon as it's available in a triple. (I'll go from quad to triple to get electronic shifting, but I'm not willing to go from quad to double.)