For everyone's benefit just spell it out.. BCN supports APRS in Android and Gaia does not support APRS. Some folks like that.
Other than that I would not say BCN is better than Gaia GPS. This is your primary complaint but rarely mention it. I can't control the internet but when people say they like or dislike something it sure is helpful to be a little more specific. If I say Gaia Sucks or Gaia is great I would take that with a grain of salt without additional information. Gaia has a larger and stronger development team. For iOS BCN has been trying for years to launch an app. It has been in Beta forever. On Android it is a popular app.
Sharing maps is not important in my opinion. See why below. I think the same can be accomplished with sharing tracks, routes, and waypoints. Something all of the apps do well. Gaia can't force download map layers to another user for a track. Meaning if I have a track that I want to share and I choose to you Gaia Topo, Wildfire map layer, cell coverage map layer, NatGeo map layer, etc when I share the track and "you" import it Gaia is not going to initiate downloading those map layers. The track data is more important than the map layers because everyone has different preferences on what they like to see. If I share a track via email I can also say "Hey download these layers once you import the track" not difficult. Everyone has different storage capacity as well. My 5 gigs of may layers for a give area or track may not work on your device.
For those new to this all of these apps are discussed in previous threads as well. Take the time to search and read in the Navigation forum.