I also forgot... cooking in vestibules is not a good idea if you are in bear country. Which sort of negates one aspect of a vestibule.

The Hilleberg with the large vestibule/storage/play area shown in the linked video doesn't really make sense to me. It's extra weight, and the compromise is that you don't get any extra space inside the tent-proper.

If you are really paranoid about your bike, then maybe there is a plus there, or you carry a huge amount of gear, or you tour in consistently bad weather.

For mine, it's just extra fabric and poles and guys and pegs that have to be accounted for when packing up.