The (dull) lighting conditions in the YouTube video aren’t ideal for showing off any paint colour at its best; ideally you’d want to see a Deep Black Pearl and a Genadilla Black GTI side by side under various different lighting conditions to make a comparison and form an objective view on which looks best. Ultimately though the mk8.5 GTI - or any mk8.5 Golf - isn’t available in Deep Black Pearl, so if you want a black mk8.5 GTI it’s Genadilla or nothing.
I’ve owned two Deep Black Pearl Golfs in the past and three other black non-VW cars before that, and what I would say is black cars are a labour of love to keep them looking good. It’s rewarding though if you put the effort in and see the results, but you do need to use a safe washing and drying technique (definitely not a sponge and wash leather!) to avoid / minimise paintwork swirls .
I’d recommend staying away from the auto car washes and the hand wash car places though, and don’t let the dealer do the free service wash if / when your car goes back to the dealership for servicing / repairs unless you like the swirled paintwork look.