Really depends who made the fake. Grey market seats are much better than the ones assembled in a cheaper
Bride has a lot of grey market seats. Recaro and Sparco don't. Bride also has zero safety testing so it doesn't really matter if they're real or not. Most 'budget friendly' aftermarket seats have zero safety ratings because they aren't really tested.
I'm ok with sitting my rump in a knock-off seat with the 2 grand I saved in my pocket. Few things feels nicer to sit on than CASH.