I prefer Touch ID, the watch can be inconsistent. It works 70% of the time on my Mac mini.. Touch ID is fast and if that’s the only reason you have blue tooth on is for the watch it makes sense not to use it.
from Macworld
2. ‘Turning off Bluetooth preserves your MacBook’s battery life.’
We detected little, if any, difference in our laptop’s energy draw with Bluetooth enabled versus with Bluetooth disabled. In fact, our MacBook Pro with SSD drew an average of 13.9W with Wi-Fi and Bluetooth off and 13.8W with Wi-Fi off but Bluetooth on.
Next, we paired a Bluetooth mouse and keyboard with our MacBook Pro with SSD, and ran the tests again. This time the power draw increased a touch to 14.3W. Looking at the OS X’s Energy Saver preferences, we noticed that the estimated battery life of the charged MacBook Pro dropped from 7 hours, 24 minutes with Bluetooth turned off to 7 hours, 5 minutes with Bluetooth turned on and the wireless keyboard and mouse paired with the system.
Takeaway: Though the meter didn’t show much change in the amount of power our laptop drew with Bluetooth off versus on, as long as nothing was paired with it, the power draw increased—and the estimated battery life decreased—when we paired a wireless keyboard and mouse with the laptop
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From Apple Support
Disabling features and technologies that use power
Mac notebooks have a number of integrated technologies which can have a significant effect on battery power.
- If you don't need Wi-Fi or Bluetooth, you can disable AirPort or Bluetooth from their menu bar icons or in System Preferences. This will help save power.
- External USB, FireWire, Thunderbolt, SD card, and Expresscard devices added to your notebook can also draw power and should be disconnected for optimal battery performance.
- Eject any CDs or DVDs from the integrated SuperDrive (if your notebook has one) to avoid the drive spinning periodically
