I don't find Touch ID all that reliable. Nor does my wife. iPhone 7 users. We both have to try multiple times to get the phone to unlock at times. Not sure why, I've deleted and re-done my fingerprint measurements many times.
So for me, Touch ID is slow and sometimes I spend a lot longer trying to unlock the phone than I want to. Perhaps Face ID will be an improvement?
However...
With Touch ID (when it works), I can unlock the phone while it's sitting next to me on the couch/table. I would imagine that with Face ID we'll have to pick up the phone, no? This seems REALLY inconvenient if so.
Truthfully, I REALLY miss the "slide to unlock". I could slide and key in my 4-digit passcode reliably (and pretty quickly) every time. Now, I have to fumble with Touch ID until it finally presents me with the option to key in my passcode.