We don’t think it is an either/or situation. Racks can compliment bikepacking bags, and vice versa. But we do think there are advantages to racks:
Cargo racks are ideal for small people with small bikes, who don’t have the frame capacity for soft bags.
Cargo racks also allow for more carrying capacity, for those of us who want to carry more food and clothing, or a trombone. Just sayin’.
Racks allow for the weight to be carried lower on the bike, which generally allows for better handling.
Racks require no adjustment to suspension settings.
Racks require no adjustment to your cockpit and do not compromise your bike fit.
Carrying a backpack that has more than a hydration pack is horribly uncomfortable for long days in the saddle and just dumb. There are less painful methods of birth control!