I’ve got Ultegra Di2 on 3 bikes, both 6800 and 8000 (which are cross-compatible), SRAM Red Etap on another, and various combinations of 105 and Ultegra on the others (yes, I have too many bikes!). The odd one out is my Holdsworth with Campagnolo Athena 3x11. Now that’s agricultural, but it looks nice. The gear range (50-39-30, 11-29) is far inferior to my main Di2 bike (50-34, 11-42).
Of the mechanical groupsets, by far my favourite is Ultegra 6600. It’s a bit limited in gear range (max 28 at the back), but the shifting is sublime. 105 7000 runs it very close, though.