I’ve been on DI2 since 2013 (9000 and 9100 series). To be fair I’ve only played with etap on a few rides in excess of 10 miles. I liked it very much but found the shifting to not be as quick or as crisp as Shimano.
mostly though, I prefer the appearance of DI2 without the bulky batteries and I ride with too many people who forget to recharge every couple hundred miles vs. the Shimano which seems to last me at least 1000 miles and doesn’t require removal of batteries to charge.
not a big deal I know. Both systems are awesome but that’s my preference.