Where is it? Wil knows and tells.
Differentiation matters. Products need to be differentiated from competitor products but also from products within their own family. For now, Apple has Face ID on three iPhone models. Older iPhones– iPhone 8 and 8 Plus, iPhone 7 and 7 Plus– have Touch ID and cost hundreds less than the new models with Face ID.
So, Face ID on more expensive products, Touch ID on less expensive products.