My main concern about using my phone for ride navigation is battery life. I don't want to be in a situation where I need my phone for an emergency with the battery drained to some extent from using it for navigation. Especially on long rides. That reason alone is why I still prefer a separate GPS unit. Secondary is all of the sensor integration (speed, cadence, HRM, power meter) which I suppose can be BT linked to the phone although it does seem like compatibility between devices is inconsistent. For example, I have had absolutely shit luck when it comes to HRM sensors. None of them seem to last very long and once the battery it came with dies, it never works right after a new battery is installed. The rechargeable Wahoo arm sensor has never been able to connect to either of my Wahoo head units, which is annoying AF. Plus, I'm not sure who the arm band is meant for, but it doesn't even fit around my non-existent biceps...