I can unlock my phone with my fingerprint while pulling it out of my pocket, so that it's ready to use as soon as my gaze falls upon it. It takes two seconds longer with face unlock - one second to get it up to my face (and make sure it's aimed in just the right spot), and another second waiting for it to actually recognize me and unlock. Easier, faster, and, hence, more usable.
The iPhone 11 has the second generation FaceID sensors which is much faster and has lower error rates (to the point that it's not very noticeable anymore). Also, while you do "lose" the TouchID sensor, all FaceID-equipped iPhones have tap to wake and raise to wake functionality which is much more useful than being able to unlock my phone in my pocket, IMO.
As far as I understand FaceID makes a "map" of your face using a series of sensors (including IR) that is then compared against with when unlocking the phone or using a FaceID compatible login in an app. The beard/facial hair is part of that map, and the way Apple designed FaceID is to learn details that slightly change over time like a beard growing. It does (from experience) fail if the change is drastic, such as shaving a long beard or being in direct sunlight when you haven't been in a long time, but you can then enter the PIN/password and it will learn the "new map data" of your face and will work during subsequent tries. I would guess it does somehow combine old and new data when you enter a PIN and update the map, as it doesn't get tripped up if you, for example, unlock your phone in direct sunlight and then unlock in lower light shortly after, but I can't be certain.
This is exactly why I bought an iPhone 8 earlier this year. The fingerprint reader combined with rest to open means my phone is ready to go before my eyes/face are anywhere near the screen. There simply is no competition (against face id) as far as speed is concerned.
