I'd rate the passat tdi DSG and the bmw 8-speed auto as equal. Deffenitely no huge difference. The huge difference is found on pricing
bmw charging 2500euro+ whereas vw charge nothing extra for it (compared to manual) atleast in my country. Heck you even get dsg + AWD for ~800euro extra compared to the std FWD and manual. Nice pricing!
It's just that DSG has been around for a while and the bmw 8-speed is new and hyped to the max so I had high expectations it would be even better, not that it would perform on par with what audi for example offered as an option in their cars like 5 years ago.
also with the bmw-8-speed I found it jumping around between gears not finding the right gear right away when hitting full throttle simulating a takeover from 80-90km/h something.
Don't mean to come off all negative about it, bottom line it's not a bad auto-gearbox but beeing "latest and greatest" with a massive pricetag it's fair to expect perfection imo.