ANT+ and Bluetooth are communication protocols that behave differently and serve different purposes. ANT+ simply broadcasts information for anyone to listen to, so you can pair 10 bike computers to the same power meter over ANT+ at the same time. 

Bluetooth uses an actual 2-way connection between devices, which allows it to change communication parameters constantly and perform better in noisy environments. Bluetooth connections were previously limited to 1 device connected to each power meter, however, with the firmware update 1.8.0, you can now connect 2 devices to your power meter via Bluetooth. 

Since the power meter is always broadcasting both ANT+ and Bluetooth, you can also connect to your power meter using multiple devices using either connection (i.e. one device over ANT+ and one device over Bluetooth).