I was recently given a pixel 3 XL, I tried so hard to get on with it but the fingerprint sensor on the back ruined it for me (and google pay on london buses is embarrassingly slow).
having the sensor on the back means you cant quickly access your phone when its sat on your desk without picking it up. its such a small thing but it made a big difference. Plus unlocking it out and about was all sorts of precarious finger gymnastics.
totally opposite problem for the iPhone in the front for me. looking at a phone beyond just finding out the time while sitting at the desk was a hassle for me. Bad angle for both phone and neck. Having the phone picked up and the censor in the front was too unnatural and required too much dexterity I didn't possess.
having the sensor on the back means you cant quickly access your phone when its sat on your desk without picking it up. its such a small thing but it made a big difference. Plus unlocking it out and about was all sorts of precarious finger gymnastics.