The finger print sensor wins the day in my book... enough for me to actually be considering switching from my current 6s Plus.
I'm not a fan of Face ID on any device and Apples take on the technology is cumbersome.
Really, did you try it? I was skeptical, much like or even more than I was before with Touch ID.
But honestly, Face ID is by far the best and most flawless implementation of a technology I've ever encountered. They nailed it.
Fingerprint? You need to actively think about that, you need to learn to put your finger on the right spot and even if it's super fast, it's a cognitive burden. You probably don't realize that, because you grow accustomed to it, but it's still there.
Face ID on the other hand is gone. It's just not there, you don't feel it, you don't see it, it vanishes. It's not discernible from having no passcode at all. I'm still stunned. I can't and I won't go back to fingerprints.