EW-WU111 adds Bluetooth and ANT+. EW-RS910 has only a charge connection for the BCR2, but the BCR2 can be used with a Windows PC and the Shimano E-Tube Project software. In other words, the BCR2 is both a charger and PC adapter. With the WU111, yes, Garmin Edge computers will show gearing and Di2 battery status. It also allows you to assign functions to the top buttons on the shifters. It works with either BT or ANT+. The WU111 can also pair to a phone and lets you use the Shimano E-Tube phone app to configure and customize (though I personally found that so unreliable I always use the BCR2 and a PC).